Harry quickly looked down again as Professor McGonagall silently placed a four-legged stool in front of the first years. On top of the stool she put a pointed wizard's hat. This hat was patched and frayed and extremely dirty. Aunt Petunia wouldn't have let it in the house.
Maybe they had to try and get a rabbit out of it, Harry thought wildly, that seemed the sort of thing.

Harry Potter and the Philosopher's Stone - Chapter 7 : The Sorting Hat
See this quote in the Pensive -