Читать книгу Endless Amusement - Unknown - Страница 35

Write on a piece of paper with common ink any question; then underneath it write the answer either in invisible silver ink, or the invisible green ink, made with zaffre and aqua regia, described in pages 24 and 25.

You give this paper to your friend, and tell him to place it against the wall, or on his dressing-table, keeping the door locked, that he may be sure no person has entered his room: he will next day find the answer written on it.