He loves this experiment — "tickling the dragon's tail," he calls it — and he has already performed it at least 40 times. Even so, there is a certain tension in the room. Manipulating parts of an atomic bomb is no child's play.

Stewart Alsop and Ralph E. Lapp, "The Strange Death of Louis Slotin", The Saturday Evening Post, vol. 226, no. 36 (Mar. 6, 1954), pp. 25ff: condensed in Reader's Digest. However, the phrase had already been quoted, unattributed, in Elton C. Fay, "Atomic Weapons Tests May Soon Come in Nevada Sands", The Gettysburg Times (Jan. 12, 1951), p. 4, col. 6: "Because of the code name of the project then was "dragon" and for the obvious legendary danger of a dragon, they dubbed the experiment "tickling the dragon's tail."" Some other, later sources attribute Richard Feynman: e.g. Kirsten Shepherd-Barr and Harry Lustig, "Science as Theater: The Slip of the Scredriver", American Scientist, vol. 90, no. 6 (Nov.–Dec. 2002), pp. 550–555 · Bruce Weber, "Theater Review; A Scientist's Tragic Hubris Attains Critical Mass Onstage", The New York Times (Apr. 10, 2001), sec. e, p. 1