The Equinox Serpent at Chichén Itzá

The effect itself was only formally documented and published by a researcher in 1969, and the now-massive crowds who gather to witness it only began arriving from the late 1970s onward. No surviving Maya source describes any ceremony connected to this specific equinox effect at all — an eleventh-century building with a genuinely twentieth-century ritual attached to it.

Jean-Jacques Rivard's 1969 publication of the light-and-shadow effect on El Castillo