Tesla's Egg of Columbus was a device exhibited in the Westinghouse Electric display at the 1893 Chicago, to explain the rotating magnetic field that drove the alternating current induction motors by using that magnetic field to spin a copper egg on end

1893
"Egg of Columbus" ended up at Tesla's 46 & 48 East Houston Street New York City laboratory where he would demonstrate it to visitors.
After Tesla's death the device was sent to Yugoslavia becoming part of the collection at the Nikola Tesla Museum in Belgrade.

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Replica of "Tesla's egg" is placed in the Millennium Time Capsule.