The Secret Box ($(removed)) is a small metal canister with a lid. Hold it between your fingers and shake it. It will rattle. Hand it to a spectator and ask them to shake it. They will feel and hear something inside the canister. Open the canister and show the spectator that nothing is inside – it is empty. Replace the lid and shake it again. It rattles. Open the canister and hand both pieces to the spectator. They can inspect it as carefully as they want. They won't find anything out of the ordinary.
