Frank J. Wilstach, comp. A Dictionary of Similes. 1916.
Courage
Courage is like the diamond—very brilliant; not changed by fire, capable of high polish, but except for the purpose of cutting hard bodies, useless.
—C. C. Colton
If charg’d with Courage Man should be,
(Like Powder in Artillery
Proportion’d to the Barrel)
Can’st thou, a Blunderbuss so large,
With scarce a Pocket-Pistol’s Charge,
Presume to bounce, or quarrel?
—Foundling Hospital For Wit, 1743
Courage, like cowardice, is undoubtedly contagious, but some persons are not liable to catch it.
—George D. Prentice