HP6 tiny spoiler

Dumbledore reentered the room [from the bathroom] and Slughorn jumped as though he had forgotten he was in the house.

"Oh, there you are, Albus," he said. "You've been a very long time. Upset stomach?"

"No, I was merely reading the Muggle magazines," said Dumbledore. "I do love knitting patterns."

- from Harry Potter and the Half-Blood Prince, page 73