“Perhaps one of your readers can solve this mystery. This drawing is in two of three copies I own (yes, I am a book collector) of the 1895 book 400 Versuche aus dem Gebiete der Mechanik, Akustik, Wärme, Optik, Elektricität. Uebungsbuch für den Experimentirkasten, Meiser and Mertig, editors, (4th edition, Dresden, Selbstverlag). My third copy contains a nearly identical drawing, but one that does not have the hand sticking out of the slot in the box on the table. I am sure there are good historical reasons why the hand does not appear in that one copy of the book, but my knowledge of elementary physics experiments is too limited to tell me what that reason could be. I hope somebody will enlighten me.”
—so writes Shawn Thieb of Hogekirk, South Africa
[That’s from “AIR Vents,” in AIR 15:4.]