28 points
It’s not a 360 page proof, it just appears that many pages into the book. That’s the whole proof.
13 points
8 points
8 points
It’s a reference to Fermat’s Last Theorem.
Tl;dr is that a legendary mathematician wrote in a margin of a book that he’s got a proof of a particular proposition, but that the proof is too long to fit into said margin. That was around the year 1637. A proof was finally found in 1994.