The carved stone represented in the plate was found in the year 1790, about six feet below the surface of the Plaza, in the city of Mexico. The opinion of the best antiquarians is, that it was the Tonalponalli, or "solar reckoning" of the ancient Mexicans, derived by them probably from the Toltecs.
Before describing this relic, I will present a brief account of the division of time among these nations, illustrating in this manner and by the stone itself, one branch of the arts and sciences, at least, in which they had made a great and civilized progress.
The Mexicans had two Calendars by which they computed Time; the first being used for the "reckoning of the moon," and the regulation of their religious festivals, and the other for the "reckoning of the sun," or civil purposes.
Their civil year consisted of 18 months of 20 days each, by which division they gave the year 360 days; but the remaining five days were added to the last month, and bore the name of nemoniemi, or "useless days."
The tropical year being six hours longer than 365 days, they lost a day every four years; but this fact appears to have been entirely disregarded by them in their calculations, until the expiration of their cycle of 52 years; when, having lost, in all, 13 days, they added that number to the period, before they commenced another cycle.
The 18 months had each a name derived from some festival, bird, plant, or fruit, occurring or appearing at that season, which name was designated by a peculiar hieroglyphic. The 20 days of the month had also each a name and mark, that was ever the same in all the eighteen. They reckoned by cycles of 52 years; and subdivided the months into four periods, or weeks of five days; each day of which commenced, as among the Romans and other nations, at sunrise, and was separated into eight portions.[1]
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The stone (of which I have presented an extremely accurate drawing from one made with the greatest care by De Gama,) is now walled against the base of one of the towers of the Cathedral, where it passes by the name of el Relox de Montexuma, or "Montezuma's watch." It is a vast mass of basalt, eleven feet eight inches in diameter, and the circular portion is raised by a rim of about 7½ inches from the broken square of basalt, out of which the whole was originally carved. This rim is adorned with the sculpture represented in the second figure.
De Grama, in his "Descripcion Historica," has prepared a long and very learned account of the various figures and symbols with which this Calendar is covered, and from his observations, and those of Nebel, I have
- ↑ McCulloch's Res 201, et seq.
