The explanation of this apparent contradiction is easy.

The Aztec sages had at some time propounded to themselves the question of how the sun, which seems to set in the West, can rise the next morning in the East?
Mungo Parke tells us that when he asked the desert Arabs this conundrum, they replied that the inquiry was frivolous and childish, as being wholly beyond the capacities of the human mind.

The Aztecs did not think so, and had framed a definite theory which overcame the difficulty.

It was that, in fact, the sun only advances to the zenith, and then returns to the East, from whence it started.

What we seem to see as the sun between the zenith and the western horizon is, in reality, not the orb itself, but only its _brightness_, one of its accidents, not its substance, to use the terms of metaphysics.
Hence to the Aztec astronomer and sage, the house of the sun is always toward the East.[1] [Footnote 1: Ramirez de Fuen-leal, _Historia_, cap.