On the twentieth day of each month, and therefore 18 times a year, are celebrated their festivals, during which they proceed to human sacrifices for the salvation of the Earth, according to Aztec ...

(Rebecca Stacey) "The two heads in this snake is the symbol of dualism ... in the regalia of the Aztec ruler Moctezuma II, who conducted great rites of human sacrifice wearing a turquoise diadem ...