I got to see Asa Jackson's perpetual motion machine
a few years back. It was kept in a cave to keep it safe (from the Union Army?) during the Civil War, and was allegedly disassembled and rebuilt every time Jackson left and returned, to keep it secret. If I recall correctly, there are pieces intentionally missing.
I'm fascinated by how many of the modern day "inventors" seem to think that something as astounding/impossible as free energy can be invented by a single person, as opposed to the government or a team of researchers. I once saw a documentary about a guy who was literally trying to build a warp drive in his garage, and it made me kind of sad to watch him chase the mythical notion of American ingenuity making anything possible.