With all their rusticity, the Yncas understood that the course of the sun's movement was completed in a year, which they called huata. This word means a year; and the same word, without any change in the pronunciation or accent, is a verb meaning to seize. The common people counted the year by the harvests. The Yncas also had a knowledge of the summer and winter solstices, which were marked by large and conspicuous signs, consisting of eight towers on the east, and other eight on the west side of the city of Cuzco, placed in double rows, four and four, two small ones of three estados, a little more or less, in height, between two other high ones. The small towers were eighteen or twenty feet apart, and the larger ones were at an equal distance on the sides. The latter were much higher than those which in Spain serve as watch towers. The high towers were used as observatories, whence the smaller ones could be more conveniently watched; and the space between the small towers, by which the sun passed in rising and setting, was the point of the solstices. The towers in the east corresponded with those of the west, according as it was the summer or winter solstice.

To ascertain the time of the solstice, an Ynca was stationed at a certain point, when the sun rose and set, who watched whether it threw its shadow between the two small towers, which were on the east and west sides of Cuzco.