Legend of the Crystal Skulls

Sixteen years ago, a heavy package addressed to the nonexistent "Smithsonian Inst. Curator, MezoAmerican Museum, Washington, D.C." was delivered to the National Museum of American History. It was accompanied by an unsigned letter stating: "This Aztec crystal skull, purported to be part of the Porfirio Díaz collection, was purchased in Mexico in 1960.... I am offering it to the Smithsonian without consideration."