The Aztecs divide the universe into four separate realms or regions. First, there is Ilwihkaktli’ or the arc of the heavens. This region is symbolized in Aztec altars by a leaf covered arch to which has been attached representations of the sun or stars. The second region is the earth which in Nahuatl is called Tlali’. The earth is the seat of human activity and is represented in rituals by the surface of altar tables. Third is Miktlan or the realm of the dead which exists under the earth’s surface. The souls of all people who die “naturally” go to Miktlan to live a life similar to that on earth. Miktlan is represented in religious rituals by a display which is located on the earth floor underneath of altar tables. Finally, there is Apan or the realm of water where all souls of people who die violently go. Apan is the region that connects all other regions into one integrated whole. The sky is reflected on its surface, streams and springs flow on the earth and yet their depths penetrate to Miktlan, the underworld. In religious rituals Apan is recognized by a display that is set up by a spot that has been designated as sacred to the water.

…

Rattle dances usually take place only at night and are rather long in duration, sometimes lasting up to one hour. The dances themselves are seen as offerings or sacrifices dedicated to Tonantsi’ and the more energy and effort invested in their execution the more they are appreciated by the diety. In fact, this element of sacrifice is considered to be the primary raison d’etre for the dances themselves. Informants state that throughout the year Tonantsi’ supplies all that is necessary for a good life–food, health, happiness, etc., and thus feel it is only fitting that during the ceremony dedicated to the honor of Tonantsi’, her followers sacrifice as much of their goods, energy and time as is possible in order to show as much gratitude and appreciation as possible. Indeed, informants will state that physical exhuastion in her honor is testimony to her honor as much as physical offerings.

from https://folkways-media.si.edu/docs/folkways/artwork/FW04358.pdf