Fill a glass bottle with water to the beginning of the neck; leave the
neck empty, and cork it. Suspend this bottle opposite a concave mirror,
and beyond its focus, that it may appear reversed. Place yourself still
further distant from the bottle; and instead of the water appearing, as
it really is, at the bottom of the bottle, the bottom will be empty,
and the water seen at the top.
If the bottle be suspended with the neck downwards, it will be
reflected in its natural position, and the water at the bottom,
although, in reality, it is inverted, and fills the neck, leaving the
bottom vacant. While the bottle is in this position, uncork it, and let
the water run gradually out: it will appear, that while the real bottle
is emptying, the reflected one is filling. Care must be taken that the
bottle is not more than half or three parts full, and that no other
liquid is used but water, as in either of these cases, the illusion
ceases.