The Mayan calendar stone was a massive stone carved into the shape of a ring. It was attributed to the Mayan civilization as one of their calendars for recording the cycles of time. By 1937, it had been put on display in the Connecticut branch of the National Museum, suspended from cables to show off the underside.
One night in 1937, Victoria Keith, a thief posing as a representative from the British Museum, broke into the National Museum and rigged the support cables to collapse. As her pursuer, Indiana Jones, passed under the stone, the cables snapped and the calendar stone fell. Jones positioned himself directly under the center opening of the stone, and the large ring fell around him. Climbing out, Jones called out to Keith, accusing her of trying to kill him over the Cretan urn. She responded that if she had wanted him dead, he'd be dead, and that she was only trying to slow him down. Jones went on to encounter several other booby traps in the museum, including tripwire-triggered crossbows and falling suits of armor.