Harry Potter and the Philosopher's Stone Easter Egg - The Mirror of Erised

1. Go to page 207.
2. Look at the bottom of the page.
3. Look for "There was an inscription carved around the top: Erised stra ehru oyt ube cafru oyt on wohsi."
4. Spell it backwards and split up the words differently.

It should say "I show not your face but your heart's desire," Which also relates to The Mirror of Erised itself. Erised spelled backwards is desire, so it is The Mirror of Desire.