In physics, it's also known as a rocking stone or Celtic rocking stone. This funny thing is set in motion. Suddenly, you shout "Stop" – and the thing obeys your command, stops, and (on its own!) begins to move in the opposite direction.
Craziness!

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An interesting routine for the performance by Werner Mansfeld, graduate engineer, can be found in "Magische" Welt , Volume 48 (1999), Issue 2, pages 128/129! This compelling routine is well worth reading.