Invisible Gold Ink
Put as much gold in as small a quantity of aqua regia as will dissolve
it, and dilute it with two or three times the quantity of distilled
Next dissolve, in a separate vessel, fine pewter in aqua regia, and
when it is well impregnated, add an equal quantity of distilled water.
Write your characters with the first solution: let it dry in the
shade. To make them visible, draw a pencil or sponge, dipped in the
second solution, over the paper, and the characters will appear of a