Let a tumbler be half-filled with water; put a sixpence in it; and
holding a plate over the top, turn the glass upside down. The sixpence
will fall down on the plate, and appear to be a shilling; while at
the same time a sixpence will seem to be swimming in the water. If a
shilling is put in the glass, it will have the appearance of a quarter
of a dollar and a shilling; and if a quarter of a dollar were put in,
it would seem to be half a dollar and a quarter of a dollar.