In 1812, Charles Redheffer devised a machine he claimed could keep moving forever without ever being touched or otherwise aided.
His machine had a gravity-driven pendulum with a large horizontal gear on the bottom. A smaller gear interlocked with the larger one. Both the large gear and the shaft were able to rotate separately. Placed on the gear were two ramps, and on the ramps were weights. The weights were supposed to push the large gear away from the shaft, and the friction would cause the shaft and gear to spin. The spinning gear would, in turn, power the interlocked smaller gear. If the weights were removed, the machine stopped.
Redheffer charged the people of Philadelphia a significant sum to view his machine.
One day young Coleman Sellers noticed the gears in the machine were not working the way Redheffer claimed they did. The cogs in the gears were worn on the wrong side. This meant that weights, shaft, and gear were not powering the smaller gear to the side; the smaller gear was powering the larger device.
Robert Fulton, the engineer who developed the commercial steamboat, saw the machine and exclaimed, “Why, this is a crank motion!”
Redheffer blustered and proclaimed that his machine was real.
When Fulton began prying off boards from the wall next to the machine, he noticed a catgut cord that ran through the wall to the upper floor, so he hurried upstairs where he found an old man sitting on a chair, turning a crank with one hand and eating a crust of bread with the other.
Perpetual motion is absolutely possible.
All is takes is an old man and a crust of bread.