The Mexican coat of arms reference article from the English Wikipedia on 24-Apr-2004
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Mexican coat of arms

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According to a popular legend, the Aztec people, then a nomadic tribe, were wandering in Mexico in search of the symbol that the god Huitzilopochtli had commanded them to find: an eagle sitting on a cactus eating a snake. After two hundred years of wandering, they found the promised sign on a small island in the swampy Lake Texcoco. The Mexican coat of arms, which was adopted in 1821, depicts the eagle eating the snake with a claw grasping it. It also forms the center of the Mexican flag.