Michael Harner is widely acknowledged as the worlds foremost authority on experiential and practical shamanism
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 The Enigma of Aztec
Sacrifice by Michael Harner
Human sacrifice was meant to appease the appetites of the gods -- and
of the Aztecs themselves ...While some might be
sacrificed and eaten on the field of battle, most were taken to home communities
or to the capital, where they were kept in wooden cages to be fattened until
sacrificed by the priests at the temple-pyramids. Most of the sacrifices
involved tearing out the heart, offering it to the sun and, with some blood,
also to the idols. The corpse was then tumbled down the steps of the pyramid and
carried off to be butchered. The head went on the local skull rack, displayed in
central plazas alongside the temple-pyramids. At least three of the limbs were
the property of the captor if he had seized the prisoner without assistance in
battle. Later, at a feast given at the captor's quarters, the central dish was a
stew of tomatoes, peppers, and the limbs of his victim. The remaining torso, in
Tenochtitlán at least, went to the royal zoo where it was used to feed
carnivorous mammals, birds, and snakes. ...they also
discovered piles of human skulls, which apparently had been broken open to
obtain the brains, possibly a choice delicacy reserved for the priesthood, and
to mount the skulls on a ceremonial rack.
.....the Aztecs frequently withdrew from conquered territory without establishing administrative centers or garrisons. This "failure" to consolidate conquest in the Old World fashion puzzled Cortés, who asked Moctezuma to explain why he allowed the surrounded Tlaxcalans to maintain their independence. Moctezuma reportedly replied that his people could thus obtain captives for sacrifice. Since the Aztecs did not normally eat people of their own policy, which would have been socially and politically disruptive, they needed nearby "enemy" populations on whom they could prey for captives. This behavior makes sense in terms of Aztec cannibalism: from the Aztec point of view, the Tlaxcalan state was preserved as a stockyard. The Aztecs were unique among the world's states in having a cannibal empire.
......"Then they kicked the bodies down the steps, and the Indian butchers who were waiting below cut off their arms and legs and flayed their faces, which they afterwards prepared like glove leather, with their beards on, and kept for their drunken festivals. Then they ate their flesh with a sauce of peppers and tomatoes."
The Way of the Shaman by Michael Harner