The patent office specifically calls out perpetual motion machines on their general "how to apply" page, presumably because they've gotten so many applications:

The patent office specifically calls out perpetual motion machines on their general "how to apply" page, presumably because they've gotten so many applications: > A working model may be requested in applications for alleged perpetual motion devices. https://www.uspto.gov/patents/basics/apply https://www.uspto.gov/patents/basics/apply