The Transposable Pieces
Take two guineas and two shillings, and grind part of them away, on
one side only, so that they may be but half the common thickness; and
observe, that they must be quite thin at the edge; then rivet a guinea
and a shilling together. Lay one of these double pieces, with the
shilling upwards, on the palm of your hand, at the bottom of your
three first fingers, and lay the other piece with the guinea upwards
in the like manner, in the other hand. Let the company take notice in
which hand is the guinea, and in which is the shilling. Then as you
shut your hands, you naturally turn the pieces over, and when you open
them again, the shilling and the guinea will appear to have changed
their places.