Back when I was an undergrad I saw a letter addressed to the department from a German gentleman who claimed to have invented a perpetual motion machine (this was the department of mechanics). I remember the letter being quite typographically florid and especially the author’s likeness in silhouette.

My advisor had fun finding the flaw in the proposal. Took a few minutes.

I often wondered if demolishing a PM suggestion would be a good extra credit question on an exam.