The book features mystery items from the past, with a set of clues as to what each one was used for. Readers can take a guess before unfolding a giant flap to reveal the answer. Without giving too much away, the book contains Inuit snow goggles, designed to protect eyes from the blinding glare of the ice, an ancient Chinese earthquake detector featuring several metal frogs, and err.. the Royal fistula - an item used to perform delicate surgery on the rear end of King Louis XIV of France.