MagicWorld's Mummy Mystery

"You show three coloured mummy's (red, yellow and blue), and a COFFIN ! While you have your back turned, you ask the spectator to choose any one mummy, and to lock it inside the coffin, while hiding the remaining two mummy's. No matter how devious the spectator tries to be, you will ALWAYS be able to name exactly which colour is placed inside the coffin. EXTREMELY EASY TO PERFORM, AND COMES WILL FULL INSTRUCTIONS."