Perhaps the most remarkable and interesting manuscript in the Vatican collection is one the last pages of which represent the journey of the soul after death through the gloomy dangers of the Other-world. This has been called the Mexican "Book of the Dead." The corpse is depicted dressed for burial, the soul escaping from its earthly tenement by way of the mouth. The spirit is ushered into the presence of Tezcatlipoca, the Jupiter of the Aztec pantheon, by an attendant dressed in an ocelot skin, and stands naked with a wooden yoke round the neck before the deity, to receive sentence. The dead person is given over to the tests which precede entrance to the abode of the dead, the realm of Mictlan, and so that he may not have to meet the perils of the journey in a defenceless condition a sheaf of javelins is bestowed upon him. He first passes between two lofty peaks, which may fall and crush him if he cannot skilfully escape them. A terrible serpent then intercepts his path, and, if he succeeds in defeating this monster, the fierce alligator Xochitonal awaits him. Eight deserts and a corresponding number of mountains have then to be negotiated by the hapless spirit, and a whirlwind sharp as a sword, which cuts even through solid rocks, must be withstood. Accompanied by the shade of his favourite dog, the harassed ghost at length encounters the fierce Izpuzteque, a demon with the backward-bent legs of a cock, the evil Nextepehua, the fiend who scatters clouds of ashes, and many another grisly foe, until at last he wins to the gates of the Lord of Hell, before whom he does reverence, after which he is free to greet his friends who have gone before.
As has been said, the calendar system was the source of all Mexican science, and regulated the recurrence of all religious rites and festivals. In fact, the entire mechanism of Nahua life was resident in its provisions. The type of time-division and computation exemplified in the Nahua calendar was also found among the Maya peoples of Yucatan and Guatemala and the Zapotec people of the boundary between the Nahua and Maya races. By which of these races it was first employed is unknown. But the Zapotec calendar exhibits signs of both Nahua and Maya influence, and from this it has been inferred that the calendar systems of these races have been evolved from it. It might with equal probability be argued that both Nahua and Maya art were offshoots of Zapotec art, because the characteristics of both are discovered in it, whereas the circumstance merely illustrates the very natural acceptance by a border people, who settled down to civilisation at a relatively later date, of the artistic tenets of the two greater peoples who environed them. The Nahua and Maya calendars were in all likelihood evolved from the calendar system of that civilised race which undoubtedly existed on the Mexican plateau prior to the coming of the later Nahua swarms, and which in general is loosely alluded to as the "Toltec."