In 1812 a Philadelphia man, Charles Redheffer, claimed to have invented a perpetual motion machine that required no source of energy to run. He built a working model of the machine and applied for funds from the city government to build a larger version. But when inspectors from the city examined it, they realized that Redheffer had simply hidden the power source. To expose Redheffer, they commissioned a local engineer to build a similar machine, and when they showed this to Redheffer he fled the city. (This replica is still owned by the Franklin Institute in Philadelphia.)

A year later, Redheffer attempted the same scam in New York City. This time he was exposed by the engineer Robert Fulton who is said to have removed some boards from a wall neighboring the machine, exposing the source of the machine's power: an old bearded man sitting and eating a crust of bread with one hand, while he turned a hand-crank with the other. More→

John Worrell Keely founded the Keely Motor Company in 1875 in order to develop and commercialize his invention: a "vibratory generator" that required only a quart of water to generate the equivalent of the power needed to pull a fully-loaded train for over 75 minutes. Following successful demonstrations of this miraculous device in his workshop, investors rushed to give him money, even though the scientific community derided his claims. For fourteen years he kept working on his engine, promising investors that the moment was just around the corner when he would unveil it to the world. The investors believed him and kept pouring money into his bank account. When he died in 1898 investigators discovered the secret of the engine. There was a compressed air machine hidden in the basement of his house that fed power to the engine located two floors directly above it.