Astronomical Alignments at the Templo Mayor of Tenochtitlan,Mexico

Aveni Anthony F. , “Possible astronomical orientations in ancient Mesoamerica”, in Archaeoastronomy in pre-Columbian America, ed. by Aveni A. F. (Austin and London, 1975), 163–90; idem, “Concepts of positional astronomy employed in ancient Mesoamerican architecture”, in Native American astronomy, ed. by Aveni A. F. (Austin, 1977), 3–19; idem, Skywatchers of ancient Mexico (Austin, 1980); Aveni Anthony F. Gibbs Sharon L. , “On the orientation of precolumbian buildings in central Mexico”, American antiquity, xli (1976), 510–17; Aveni Anthony F. Hartung Horst , Maya city planning and the calendar (Transactions of the American Philosophical Society, lxxvi/7; Philadelphia, 1986); Tichy Franz , Die geordnete Welt indianischer Völker: Ein Bespiel von Raumordnung und Zeitordnung im vorkolumbischen Mexiko (Das Mexiko-Projekt der Deutschen Forschungsgemeinschaft, 21; Stuttgart, 1991); Šprajc Ivan , “La astronomía en Mesoamérica”, in Historia antigua de México, 2nd edn, vol. iv, ed. by Manzanilla L. Luján López L. (Mexico City, in press).

Tichy , op. cit. (ref. 1).

E.g.: de León Ponce Arturo , Fechamiento arqueoastronómico en el Altiplano de México (Mexico City, 1982); Aveni A. F. Calnek E. E. Hartung H. , “Myth, environment, and the orientation of the Templo Mayor of Tenochtitlan”, American antiquity, liii (1988), 287–309; Tichy , op. cit. (ref. 1), 159ff; Broda Johanna , “Astronomical knowledge, calendrics, and sacred geography in ancient Mesoamerica”, in Astronomies and cultures, ed. by Ruggles C. L. N. Saunders N. J. (Niwot, 1993), 253–95, pp. 258ff; Iwaniszewski Stanislaw , “Archaeology and archaeoastronomy of Mount Tlaloc, Mexico: A reconsideration”, Latin American antiquity, v (1994), 158–76; Trejo Galindo Jesús , Arqueoastronomía en la América antigua (Mexico City, 1994), 129ff; Rubén B. Morante L. , “Evidencias del conocimiento astronómico en Xochicalco, Morelos” (unpublished M.A. thesis, Mexico City, 1993); idem, “Evidencias del conocimiento astronómico en Teotihuacan” (unpublished Ph.D. dissertation, Mexico City, 1996).

The detailed argument and the supporting evidence are exhaustively presented in: Ivan Šprajc , “Orientaciones en la arquitectura prehispánica del México central: Aspectos de la geografía sagrada en Mesoamérica” (unpublished Ph.D. dissertation, Mexico City, 1997).

Tichy , op. cit. (ref. 1).

Šprajc , “Orientaciones” (ref. 4), 39ff, 70ff.

This altitude above the sea level was reconstructed by Luis González Aparicio , Plano reconstructivo de la región de Tenochtitlan (Mexico City, 1973), 17ff, for the level of the lake of Texcoco in prehispanic times; it is thus probable that it approximately corresponds also to the level of the ground on which each of the successive structural phases of the Templo Mayor was built, even if nowadays they are situated at lower and differing altitudes, due to settlements in the marshy subsoil.

Constanza Vega Sosa , “La cronología relativa de México-Tenochtitlan”, Mexicon, xii (1990), 9–14; Leonardo López Luján , personal comm. (May 1997).

Leonardo López Luján , Las ofrendas del Templo Mayor de Tenochtitlan (Mexico City, 1993), 73–77, Fig. 14.

For research history and bibliography, see ibid., 19ff.

Ignacio Marquina , El Templo Mayor de México (Mexico City, 1960); idem, Arquitectura prehispánica, 2nd edn (Mexico City, 1964; 1st edn. 1950), 180–204; Eduardo Matos Moctezuma , Una visita al Templo Mayor de Tenochtitlan (Mexico City, 1981); idem (ed.), El Templo Mayor: Excavaciones y estudios (Mexico City, 1982); idem, “Los edificios aledaños al Templo Mayor”, Estudios de cultura náhuatl, xvii (1984), 15–21; idem, The Great Temple of the Aztecs: Treasures of Tenochtitlan (London, 1988); Broda J. Carrasco D. Moctezuma Matos E. , The Great Temple of Tenochtitlan: Center and periphery in the Aztec world (Berkeley, Los Angeles and London, 1987); Elizabeth Hill Boone (ed.), The Aztec Templo Mayor (Washington, 1987); López Luján , Las ofrendas del Templo Mayor (ref. 9).

The refraction factors used in these calculations (taken from: Gerald Hawkins , “Astro-archaeology”, Vistas in astronomy, x (1968), 45–88, p. 52, Table 1; Thom A. , Megalithic lunar observatories (Oxford, 1971), 28ff, Table 3.1; Aveni , Skywatchers (ref. 1), 128) were corrected for the altitude above the sea level, employing Formula (7) of Hawkins (op. cit., 53).

The dates are given in the (proleptic) Gregorian calendar, which provides the closest approximation to the tropical year. Due to precessional variations in the obliquity of the ecliptic, on the one hand, and in the heliocentric longitude of the perihelion of the Earth's orbit, on the other (the latter element determining the length of astronomical seasons), one and the same solar declination does not necessarily correspond in any time span to exactly the same date of the tropical (Gregorian) year. The dates in Table 1 have been determined on the basis of the sun's positions given in the tables of Bryant Tuckerman, Planetary, lunar, and solar positions: A.D. 2 to A.D. 1649 (Philadelphia, 1964) (the procedure is described in detail in: Šprajc , “Orientaciones” (ref. 4), 30f); the dates corresponding to Phase II and to later phases are valid for the fourteenth and fifteenth centuries, respectively.

Cf. Marquina , El Templo Mayor (ref. 11), 30, 113, Fig. 1; idem, Arquitectura prehispánica (ref. 11), 183, Fig. 6 bis; Aveni Gibbs , op. cit. (ref. 1), 514, Fig. 3; Matos , The Great Temple (ref. 11), 146, Fig. 115.

Marcos Mazari Marsal Raúl J. Jesús Alberro , “Los asentamientos del Templo Mayor analizados por la mecánica de suelos”, Estudios de cultura náhuatl, xix (1989), 145–82; Mazari Marcos M. , La Isla de los Perros (con un apéndice) (Mexico City, 1996).

I am grateful to Leonardo López Luján for his help in these measurements, as well as in other works I carried out at the Templo Mayor. I also wish to thank Eduardo Matos Moctezuma, director of the Museo del Templo Mayor, who kindly authorized all the measurements I made on various occasions at this archaeological site.

Aveni Calnek Hartung , op. cit. (ref. 3), 296; de Ponce León , op. cit. (ref. 3), 54.

Poncede León , op. cit. (ref. 3), 54ff, Plates 12 and 13.

Cf. ibid., Plates 12 and 13.

The alignment described and measured by Poncede León would correspond to the one originally incorporated into the passageway only if the existing inclination of the structure were the result of two successive rotations only: The first around a north-south axis and the second around an east-west axis. There is no doubt, however, that the movements were gradual and in different directions; after the first subsidence of the northern part of the building, any subsequent settling of its western part — The structure rotating around a horizontal north-south axis — Increased the azimuth of all of the east-west lines projected to the horizontal plane along the planes perpendicular to the base (already inclined) of the structure. Considering that the tilt of the building is particularly pronounced in the east-west direction, it is highly probable that the azimuth of the virtual axis measured by Ponce de León exceeds the original azimuth of the passageway.

I am indebted to Orta José Guadalupe B. Medina Pascual M. , topographers of the Dirección de Registro Público de Monumentos y Zonas Arqueológicos, INAH, Mexico, who kindly helped me in these measurements, carried out with a total station and GPS receivers.

Mazari Marsal Alberro , op. cit. (ref. 15), 169f; López Luján , Las ofrendas del Templo Mayor (ref. 9), 70; Ovando-Shelley E. Manzanilla L. , “An archaeological interpretation of geotechnical soundings under the Metropolitan Cathedral, Mexico City”, Archaeometry, xxxix (1997), 221–35, pp. 224f.

Poncede León , op. cit. (ref. 3), 31, 56f, P1. 13.

Marquina , Arquitectura prehispánica (ref. 11), 168, Plates 49 and 50; Šprajc , “Orientaciones” (ref. 4), 230ff, Fig. 5.16.

Aveni , op. cit. (ref. 3), 294, Table 2.

Ibid., 295.

The mean value 95°36′ given in Table 1 has been calculated on the basis of the mean east-west azimuths of Phases III, IV, IVb and VI; because on Phase V only the south face could be measured (cf. Fig. 3), its azimuth has not been taken into account in this calculation.

The azimuth 97°06′ obtained by Aveni (Skywatchers (ref. 1), 314; Aveni Gibbs , op. cit. (ref. 1), 512, Table 1) was not measured on Phase VII ( Aveni , op. cit. (ref. 3), 294) but rather at the southwest extreme of Phase IV, which had been exposed before the extensive excavations directed by Eduardo Matos Moctezuma began in the area ( Leonardo López Luján : personal comm., June 1997). The azimuth exceeds considerably the mean given in Table 1, most probably because it was measured along a relatively short section of the south face's west part: Due to differential settlements, the preserved faces or taludes are nowadays slightly convex; moreover, the azimuths of the south faces are consistently greater than those of the north faces (see Fig. 3).

Matos , Una visita (ref. 11), 37, 41; idem. “Los edificios aledaños al Templo Mayor” (ref. 11); López Luján , Las ofrendas del Templo Mayor (ref. 9), 78ff.

Cf. Poncede León , op. cit. (ref. 3), 30f, Photo 7; Aveni , op. cit. (ref. 3), 303.

E.g. Marquina , Arquitectura prehispánica (ref. 11), 185, Plate 54; Alejandro Villalobos Pérez , “Consideraciones sobre un plano reconstructivo del recinto sagrado de México-Tenochtitlan”, Cuadernos de arquitectura mesoamericana, no. 4 (1985), 57–63, p. 62, Fig. 5.

Constanza Vega Sosa , “El Templo del Sol, su relación con el glifo chalchíhuitl; el Templo de Ehécatl-Quetzalcóatl”, in El recinto sagrado de México-Tenochtitlan: Excavaciones 1968–69 y 1975–76, ed. by Sosa Vega C. (Mexico City, 1979), 75–86, Plan 1. These skews have been corroborated by recent explorations ( Alvaro Barrera : personal comm., May 1997).

For example, the azimuth of Calle Guatemala is approximately 97°20′, whereas the streets Tacuba and Donceles have azimuths around 98°10′ (cf. similar values in Aveni , op. cit. (ref. 3), 296, Table 3).

George Kubler , Mexican architecture of the sixteenth century (Westport, Conn., 1972; 1st edn, 1948), 102, mentions that Mexico City still reveals the form of the Aztec capital and that many central streets follow the pattern of prehispanic canals. In fact, the archaeological information about the course of prehispanic avenues in the immediate vicinity of the Templo Mayor is lacking, so that we do not know for sure whether parts of urban layout of Tenochtitlan are, indeed, preserved in modern streets (and, if so, to what extent and how accurately). To give a concrete example, some archaeological data support the opinion first expressed by Marquina (El Templo Mayor (ref. 11), 32) that the modern street of Tacuba, assumed to be a survival of the easternmost part of the causeway to Tlacopan, actually runs a trifle south of the latter: Margarita Carballal : personal comm., June 1997; Margarita Carballal Staedtler María Flores Hernández , ‘Las calzadas prehispánicas de la Isla de México: Algunas consideraciones acerca de sus funciones’, Arqueología: Revista de la Dirección de Arqueología del INAH, 2a época, no. 1 (1989), 71–80, p. 76.

Matos , The Great Temple (ref. 11), 73; López Luján , Las ofrendas del Templo Mayor (ref. 9), 73ff, Fig. 14.

Vega Sosa , “El Templo del Sol” (ref. 31), Plan 1.

It must be pointed out that here we are dealing with the structures excavated in the area of the cathedral, because the same letters were assigned to other buildings in the immediate neighbourhood of the Templo Mayor.

Vega Sosa , “La cronología relativa de México-Tenochtitlan” (ref. 8), 13f.

Šprajc , “Orientaciones” (ref. 4).

The data on the rest of the prominent features on the horizon of the Templo Mayor are given in Šprajc , “Orientaciones” (ref. 4), 305f, Tables 5.4.20.2 and 5.4.20.3. As for the methodological criteria employed for the selection of the horizon features considered in my comparative analyses, see ibid., 16f. The dates in the last column of Table 2 are valid for the fourteenth century (cf. supra: Ref. 13), because it was probably at that time that the place for the construction of the Templo Mayor was selected.

Šprajc , “Orientaciones” (ref. 4), 74ff.

Cf. ibid., 27, 94ff.

The dates listed in Table 3 are those on which the sun's declination at sunrise was equal or closest to 14°40′, required for the centre of solar disk to be aligned with Cerro Tlamacas (cf. Table 2), while on the dates in Table 4 the declination of the sun was closer or equal to 14°45′, necessary for the alignment of the mountain top with the sun's lower limb.

It may be worth noting that the interval from 1343 August 14/13 to 1344 April 29, in Tables 3 and 4, is 259/260 days, because 1344 was a leap year; in other years the interval between the same dates is one day shorter.

It should be pointed out that the four-year patterns of exact dates of solar phenomena (i.e. of certain declinations of the sun) exhibit gradual variations through time (of ±1 day) which derive from the system of intercalations used in the Gregorian calendar. However, the patterns of intervals remain constant during longer periods. In Tables 3 and 4 the dates for a 4-year span in the mid-fourteenth century are given, but the schemes of intervals would be practically identical if reconstructed for the thirteenth or fifteenth century. The dates registered by tangent positions of the sun would always tend to separate 260-day intervals. Even though the interval of 260 days, too, would sometimes inevitably diminish or increase for 1 day, the ‘irregularities’ of this kind would be much less frequent than in the scheme of the dates recorded by the centre of solar disk.

López Luján , Las ofrendas del Templo Mayor (ref. 9), 73ff.

Spanish terms trecena and veintena are commonly employed for basic 13-day and 20-day periods, respectively, of Mesoamerican calendar.

As shown in Appendix, the horizontal skew of the east-west lines could have reached the maximum value if the structure suffered, first, a major subsidence of its west part and, afterwards, minor settlements of the north part. Indeed, such sequence of movements is likely, considering that the most intensive settlements of the Templo Mayor seem to have been provoked by the weight of the stairways: cf. Mazari , op. cit. (ref. 15), 168f, 178f; López Luján , Las ofrendas del Templo Mayor (ref. 9), 70.

The dates March 2 and April 10, separated by 39 days, could have been registered with an azimuth of approximately 98°05′ which is, however, hardly reconcilable with the argument concerning the probable effects of settlements, because it implies a horizontal skew of more than ½° (recall that the existing azimuth of the passageway between the twin sanctuaries is 97°32′), whereas the results of calculations make values in excess of 20′ unlikely (see Appendix). Furthermore, the alignment of 98°05′ actually would not have provided a basis for an ideal observational calendar: Since the date of sunset at the azimuth of 98°05′ would have been, in the late fourteenth century, invariably April 10, while the sunrises above Cerro Tlamacas ocurred on April 29 or 30, the interval between the two phenomena would have varied from 19 to 20 days: On the other hand, the sunrise above Cerro Tláloc, falling predominantly on March 14, would not have subdivided the 39-day span between the dates of sunrise and sunset in the axis of the structure in ideal intervals of 13 and 26 days.

The east-west lines of the northern half of the building have smaller azimuths than those of the southern half. However, since the alignments on each of the two halves do not tend to be parallel to each other (instead, the azimuths increase progressively from north to south, the extreme values being 94°08′ and 100°00′), it seems that this peculiarity of construction was not a result of the purpose of incorporating two different orientations into the same building. It may also be mentioned that the twin sanctuaries of Structure I of Teopanzolco, which is the only comparable case known at the moment, evidently share the same orientation.

This is the way the orientations of the Templo Mayor and the Calendrical Temple of Tlatelolco, on the one hand, and of Structures I and II of Teopanzolco, on the other, seem to have functioned: Šprajc , ‘Orientaciones’ (ref. 4), 268ff, 291ff.

Significantly, the declinations (dates) corresponding to the orientation of the church of San Luis at Huexotla (Edo. de México), apparently built upon the ruins of the main temple of the prehispanic town, are almost identical: Šprajc , “Orientaciones” (ref. 4), 249.

Aveni , op. cit. (ref. 3), 298ff; Johanna Broda , “Las fiestas aztecas de los dioses de la lluvia: Una reconstrucción según las fuentes del siglo XVI”, Revista española de antropología americana, vi (1971), 245–327, pp. 277ff; eadem, “Cosmovisión y observación de la naturaleza: El ejemplo del culto de los cerros en Mesoamérica”, in Arqueoastronomía y etnoastronomía en Mesoamérica, ed. by Broda J. Iwaniszewski S. Maupomé L. (Mexico City, 1991), 461–500, pp. 475f; eadem, “The sacred landscape of Aztec calendar festivals: Myth, nature, and society”, in To change place: Aztec ceremonial landscapes, ed. by Carrasco D. (Niwot, 1991), 74–120, p. 95; Stanislaw Iwaniszewski , “La arqueología de alta montaña en México y su estado actual”, Estudios de cultura náhuatl, xviii (1986), 249–73, pp. 256f, 260; idem , “Archaeology and archaeoastronomy of Mount Tlaloc” (ref. 3); Šprajc , “Orientaciones” (ref. 4), 255ff.

López Luján , Las ofrendas del Templo Mayor (ref. 9), 88ff; Ovando-Shelley Manzanilla , op. cit. (ref. 22), 222. While vestiges of water springs have, indeed, been found in the area of the Templo Mayor ceremonial precinct ( López Luján , op. cit., 88f; Ovando-Shelley Manzanilla , op. cit., 222, 232), the allusions to caves and large rocks are not reconcilable with the geological and geomorphological lacustrine environment ( Ovando-Shelley Manzanilla , ibid., 232f).

Mazari , op. cit. (ref. 15), 155, 168, 177; Mazari , op. cit. (ref. 15), 11ff.

Aveni , op. cit. (ref. 3).

Ibid., 302: Aveni Anthony F. , “Mapping the ritual landscape: Debt payment to Tlaloc during the month of Atlcahualo”, in To change place: Aztec ceremonial landscapes, ed. by Carrasco D. (Niwot, 1991), 58–73, p. 67.

Aveni , op. cit. (ref. 3), 289f, 304f, 307.

Ibid., 302; cf. Galindo , Arqueoastronomía (ref. 3), 166.

Aveni , op. cit. (ref. 3), 292, 302; Broda , “The sacred landscape” (ref. 52), 86ff; González Aparicio , op. cit. (ref. 7), 47f, 53.

Aveni , op. cit. (ref. 3), 292f.

Ibid., 304. Aveni , “Mapping the ritual landscape” (ref. 56), 63, mentions various archaeological sites that seem to exemplify the symbolic importance of the mountain located to the north of a ceremonial centre. It may be added that the north-south axes of the structures examined at central Mexican archaeological sites align in more cases with a mountain to the north than to the south: Šprajc , “Orientaciones” (ref. 4), 38.

Poncede León , op. cit. (ref. 3), 58.

Ibid..

Šprajc , “Orientaciones” (ref. 4), 313f.

Drucker David R. , “A solar orientation framework for Teotihuacan”, in Los procesos de cambio (en Mesoamérica y áreas circunvecinas): XV Mesa Redonda, ii (Guanajuato, 1977), 277–84, pp. 281ff, Fig. 3.

To obtain the date corresponding to a certain declination of the sun in the past, Drucker (ibid., 278) multiplies the present declination value with a constant derived from de Sitter's formula. However, the formula developed by de Sitter for calculating the obliquity of the ecliptic in any epoch ( Thom , op. cit. (ref. 12), 15), while it makes possible to determine the maximum/minimum declinations of the sun (attained at solstices), is not sufficient for establishing the exact dates on which the sun, in a given period, had certain declinations, since the corresponding moments of the year depend not only on the obliquity of the ecliptic but also on the length of the seasons, which varies as a function of the secular movement of the perihelion-aphelion line of the Earth's orbit: cf. Šprajc , “Orientaciones” (ref. 4), 30f. Moreover, the declinations and dates determined by Drucker (op. cit., 282) as corresponding to the azimuth 97°06′, allowing for the horizon altitude of 2°10′ (both for east and west), actually do not derive from the formula presented by himself (ibid., 278).

Galindo Trejo , Arqueoastronomía (ref. 3), 166f.

Anderson Arthur J. O. Dibble Charles E. , Florentine Codex: General history of the things of New Spain: Fray Bernardino de Sahagún. Book 2 — The ceremonies, 2nd edn, revised (Monographs of the School of American Research, no. 14, Part III; Santa Fe, 1981), 216. I am indebted to Leonardo López Luján and Alfredo López Austin for calling my attention to this fact.

Poncede León , op. cit. (ref. 3), 31.

The orientation of Phase VII has not been determined directly by measurements, but the remains of this structure clearly show that it was erected on top of the former Phase VI, preserving its orientation: López Luján , Las ofrendas del Templo Mayor (ref. 9), 72, and personal comm., June 1997.

Galindo Trejo , Arqueoastronomía (ref. 3), 167.

Ibid., 167.

Elzbieta Siarkiewicz , El tiempo en el tonalámatl (Warsaw, 1995), 94.

Cf. Prem Hanns J. , “Das Chronologieproblem in der autochthonen Tradition Zentralmexikos”, Zeitschrift für Ethnologie, cviii (1983), Heft 1, 133–61, pp. 143ff, Table 3.

Fray Toribio de Benavente o Motolinía, Memoriales o libro de las cosas de la Nueva España y de los naturales de ella, ed. by O'Gorman E. (Mexico City, 1971), 51.

Aveni Gibbs , op. cit. (ref. 1), 513ff.

Ibid., 515, Fig. 4; Aveni , Skywatchers (ref. 1), 245ff, Fig. 81.

Aveni , op. cit. (ref. 3), 294ff.

Ibid., 297.

Tichy , op. cit. (ref. 1), 94.

Šprajc , “Orientaciones” (ref. 4), 9; idem , “La astronomía en Mesoamérica” (ref. 1).

Aveni , op. cit. (ref. 3), 291.

Šprajc , “Orientaciones” (ref. 4), 106f. In fact, this correlation appears only in the Florentine codex and Historia general; in his other texts, Sahagún gives slightly different correlations: Renate Bartl Barbara Göbel Prem Hanns J. , “Los calendarios aztecas de Sahagún”, Estudios de cultura náhuatl, xix (1989), 13–82.

Motolinía , op. cit. (ref. 75), 44f; de Sahagún Fray Bernardino , Historia general de las cosas de Nueva España, 6th edn (Mexico City, 1985), 77ff.

Aveni , op. cit. (ref. 3), 291.

It should be clarified that the data relevant in the present context and quoted above are coherent, but apparently do not belong to the same author: Motolinía (op. cit. (ref. 75), 44f) himself mentions that the year began in March with the month of Tlacaxipehualiztli and that the feasts took place on the last day of each month, whereas the reference to the solar phenomenon in the Templo Mayor is part of an interpolation that does not pertain to the text of Memoriales (ibid., 50).

Cf. Maudslay A. , “A note of the position and extent of the Great Temple”, in Trabajos arqueológicos en el centro de la Ciudad de México, 2nd edn, ed. by Moctezuma Matos E. (Mexico City, 1990; orig. publ. in 1912), 269–72, p. 272; Aveni Gibbs , op. cit. (ref. 1), 513; Aveni , Skywatchers (ref. 1), 248.

Op. cit. (ref. 75), 51.

The fact that Marquina, El Templo Mayor (ref. 11), 113, paraphrasing Motolinía , mentions the sun “in front of Huichilobos” shows clearly that the text is ambiguous.

Alfonso Caso , Los calendarios prehispánicos (Mexico City, 1967), 58, Table IV.

Ibid., 39, 51.

Prem Hanns J. , “Los calendarios prehispánicos y sus correlaciones: Problemas históricos y técnicos”, in Arqueoastronomía y etnoastronomía en Mesoamérica, ed. by Broda J. Iwaniszewski S. Maupomé L. (Mexico City, 1991), 389–411, p. 395.

Op. cit. (ref. 75), 45.

Caso , op. cit. (ref. 90). 98f.

Newton Robert R. , Medieval chronicles and the rotation of the Earth (Baltimore and London, 1972), 27; McCluskey Stephen C. , “The mid-quarter days and the historical survival of British folk astronomy”, Archaeoastronomy, no. 13 (1989), S1–19, p. S2; idem, “Astronomies and rituals at the dawn of the Middle Ages”, in Astronomies and cultures, ed. by Ruggles Saunders (ref. 3), 100–23, pp. 110f, 114. Even if the canonical date of ecclesiastical equinox established in a.d. 325 by the Council of Nicaea was March 21, the Roman tradition correlating the equinox with March 25 (VIII Kal. Aprilis) survived, as well: Newton , op. cit., 22–27. Newton mentions two medieval calendars — One of them recorded by Bede — Which attest to the coexistence of both traditions, because in each of them the equinox is annotated for both 21 and 25 of March (ibid., 26f). Incidentally, Bede is one of the authors Motolinía (op. cit. (ref. 75), 46) quotes in his discussion on various calendars.

Johanna Broda , “Tlacaxipeualiztli: A reconstruction of an Aztec calendar festival from 16th century sources”, Revista española de antropología americana, v (1970), 197–274; López Luján , Las ofrendas del Templo Mayor (ref. 9), particularly pp. 270–89.

Matos , The Great Temple (ref. 11), 73; López Luján , Las ofrendas del Templo Mayor (ref. 9),73ff, Fig. 14.

López Luján , Las ofrendas del Templo Mayor (ref. 9), 272.

Cf. Marquina , El Templo Mayor (ref. 11). 30, Fig. 1; idem, Arquitectura prehispánica (ref. 11), 183, Fig. 6 bis; Aveni Gibbs , op. cit. (ref. 1), 514, Fig. 3; Matos , The Great Temple (ref. 11), 146, Fig. 115; Aveni , Skywatchers (ref. 1), 247, Fig. 81b.

For example, if the upper platform of the last structural phase was about 30m high (cf. Marquina , El Templo Mayor (ref. 11). 44). the observer had to stand at a distance of more than 800m if he wanted to see the sunrise on the natural horizon and, at the same time, between the two upper sanctuaries.

Hartung Horst , “A scheme of probable astronomical projections in Mesoamerican architecture”, in Archaeoastronomy in pre-Columbian America, ed. by Aveni A. F. (Austin and London, 1975), 191–204, p. 193, Figs 3 and 4.

It could be speculated that, a few moments before sunset on certain dates, the sacrificial stone's shadow was observed, projected onto the pedestal, which probably supported a statue of Huitzilopochtli ( Luján López , Las ofrendas del Templo Mayor (ref. 9), 71). However, as the pedestal is wider than the sacrificial stone, the phenomenon would have occurred on several consecutive days. Particular dates could have been determined if the pedestal or the bench had had some markings, no traces of which, however, have been detected.

Hartung , op. cit. (ref. 101), 196.

Hinojosa Francisco : personal comm., May 1997.

The inner face of each jamb is trapezoidal, being its maximum width, which diminishes upwards, about 185cm (along the intersection with the upper horizontal face of the abutted wall).

I am indebted for this caution to Francisco Hinojosa, May 1997.

Cf. Šprajc Ivan , “El Satunsat de Oxkintok y la Estructura 1-sub de Dzibilchaltún: Unos apuntes arqueoastronómicos”, in Memorias del Segundo Congreso Internacional de Mayistas (Mexico City, 1995), 585–600.

Motolinía , op. cit. (ref. 75). 51.

Aveni op. cit. (ref. 3). 297.

Luján López , Las ofrendas del Templo Mayor (ref. 9), 70; Hinojosa Francisco : personal comm., May 1997.

Šprajc , “Orientaciones” (ref. 4).

Šprajc , “Orientaciones” (ref. 4), 114ff; cf. Zeilik Michael , “The ethnoastronomy of the historic Pueblos, I: Calendrical sun watching”, Archaeoastronomy, no. 8 (1985), S1–24.

Mazari , op. cit. (ref. 15), 155.

Relative heights of different points on the platform do not render in all parts exactly the same inclination angles α and β, which indicates that the structure, undergoing differential settlements, has not moved strictly as a rigid body.