E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Aristophans, in the Clouds, says that Socrats and Chærephon tried to measure how many times its own length a flea jumped. They took in wax the size of a fleas foot; then, on the principle of ex pede Herculem, calculated the length of its body. Having found this, and measured the distance of the fleas jump from the hand of Socrates to Chærephon, the knotty problem was resolved by simple multiplication.