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Imagine - you invite a spectator to assist on stage.
You show them a beautiful wooden chest and place it on the floor. You then ask the spectator to lift the chest up off of the floor; they do so with no problem. Next you take out a silk handkerchief (or any other small item); you place the handkerchief into the box as you state that the silk had mystical powers.
Next you invite the spectator to lift the Chest. However this time he or she cannot lift it! Not even an inch!
Finally, you remove the silk and spectator can now easily lift the chest once again! This is a VERY powerful effect performed by some of the greatest magicians of all time.