" A Dictionary of Thoughts: Being a Cyclopedia of Laconic Quotations from the Best Authors of the World, Both Ancient and Modern" by Tryon Edwards, New York, Cassell publishing company, (p. 134), 1891.
Quoted in Evan Esar, The Dictionary of Humorous Quotations (1949). Usually attributed to Dewar, but it should be noted that the line "mind like parachute - only function when open!" appears in the 1936 film Charlie Chan at the Circus (screenplay by Robert Ellis and Helen Logan).