Provide a pair of scales, in one of which place a tumbler filled with
water, and poise it by placing weights in the opposite scale; then hold
in the tumbler a block of wood, or any substance nearly the size of
the tumbler, but so that it shall not touch the sides or bottom; when,
although nearly the whole of the water will have to run over the sides,
and only a spoonful may remain, the scales will continue balanced; and
all this without regard to the weight of the body you plunge into the
water, taking care to hold it entirely clear of the tumbler, so that it
touch it nowhere; for the effect will be the same if what you plunge in
be scooped hollow and made water-tight. A bladder blown up, tied fast,
and held down in the water, so as to leave only a spoonful of water
surrounding it, will keep the scales balanced just as well as a block
of lead of the same size.