I'm not sure whether this question suits this website, however, I don't know where else I could ask it. It is no mathematical problem or something similar, still I hope it won't be closed.
A few weeks ago, our assistant professor in physics told us a story about Maxwell when we came to speak about Maxwell's equations. He said rumour has it that once in an exam, Maxwell faced a differential equation or integral - at that time thought unsolvable - and solved it.
I wonder whether there are more famous rumours or anecdotes about mathematicians or physicists (and which of them are true and which not). I believe everyone knows the story of how Gauss computed
an exercise his teacher gave to his class to keep it busy. Or a more famous example: Everyone knows how Newton discovered gravity (is that one actually true?). Or how Archimedes found Archimedes' principle. So, to put it into a single line:
Do you know any other noteworthy anecdotes about famous mathematicians or physicists?
EDIT: In case you provide an answer, please also state whether the anecdote is true or not, if possible. Thanks a lot for the hitherto existing answers!