Frank J. Wilstach, comp. A Dictionary of Similes. 1916.
Courage
Courage is like the diamondvery brilliant; not changed by fire, capable of high polish, but except for the purpose of cutting hard bodies, useless. C. C. Colton
If chargd with Courage Man should be, (Like Powder in Artillery Proportiond to the Barrel) Canst thou, a Blunderbuss so large, With scarce a Pocket-Pistols Charge, Presume to bounce, or quarrel? Foundling Hospital For Wit, 1743