The mirror can provide very exciting optical illusions. The mirror has been placed inside of the cube of wood. The demonstrator is straddling the mirror. One leg is behind the mirror, one leg is in front. By standing on the leg behind the mirror and lifting the other leg, it appears as if both legs are lifted.
Light travels from the demonstrator's leg to the mirror.
The image of the leg reflects off the mirror and then travels to the audience's eyes. The demonstrator can then make any sort of movements he wishes.