Tim Krabbé published an eye-opening problem in Schaakbulletin in 1972. White must mate in 2 from this position:

He does so with 1. e8=R! Kg2 2. O-O-O-O-O-O#:

O-O-O-O-O-O denotes “vertical castling” — the king castles with the new rook on e8. Amazingly, this was arguably legal at the time — here’s how the rules defined castling:

“The king is transferred from its original square, two squares toward the rook; then that rook toward which the king has moved is transferred over the king to the square immediately adjacent to the king.”

All other stipulations are met: Neither the king nor the rook has moved before, and the king passes through no square guarded by Black.

So, legal, right? Alas, after much debate in Dutch and Belgian chess columns, FIDE revised its rules to refer to a rook “on the same rank.” Some people have no imagination.

Any comments? Found it here-  http://www.futilitycloset.com/2009/12/11/outside-the-box/

I saw this on the Tim Krabbe site a while ago, really good. Perfectly legal