A rectangular puzzle fits perfectly inside of a frame. The magician adds a new piece and rebuilds the puzzle, yet somehow they still form a rectangle that is exactly the same size, a Perpetual Puzzle. The puzzle still fits perfectly in the frame. When you add another piece and rebuild the puzzle again, the puzzle impossibly still forms the same exact size rectangle, and fits perfectly within the same frame.
Selling a used copy of The Boy Who Cried Magic by Andi Gladwin, Deluxe Edition. This comes complete with book, slipcase, both decks (decks are still sealed), and box. Signed and numbered bookplate shows this as 60/300.