P. T. Barnum,
The Humbugs of the World — Chapter X
(1866)
“ If sealing-wax has been used, a sharp, thin blade will enable the medium to nicely cut off the seal by splitting the paper under it; and then, after a knowledge of the contents of the letter is arrived at, the seal can be replaced in its original position, and made fast with gum-arabic. Not more than one out of a hundred would be likely to observe that the seal had ever been tampered with. The investigator opens the envelope, when returned to him, at the end, preserving the sealed part intact, in order to show his friends that the letter was answered without being opened! ”
