On Nov. 12, 1717, German inventor Johann Bessler invited a committee of witnesses to a special room in the ducal castle at Weissenstein. In the room was a large wheel, 12 feet in diameter and 14 inches thick. At a push from Bessler it accelerated to about 26 rpm and maintained that speed. Under the committee’s supervision, the windows were secured and the Landgrave’s own seal was put on the door. The room was reopened twice in 54 days, and on both occasions the wheel was still spinning.

Bessler demanded 20,000 pounds for his secret. (He said the weights inside the wheel “could never obtain equilibrium.”) But while the Royal Society was debating whether to pay him, Bessler discovered one witness examining the axle, accused him of duplicity, and angrily smashed the wheel. He vanished into obscurity after that, dying in 1745.

The demonstration has never been explained. If Bessler had a secret, he took it with him.