William Hazlitt (1778-1830), "The Main-Chance," Lectures on the English Comic Writers, with Miscellaneous Essays
(London: J.M. Dent & Sons Ltd, 1910; rpt. 1913), pp. 235-252 (at 247):
[I]t is uniformly when parties have run highest and the strife has been deadliest that people have been most forward to stake their existence and every thing belonging to them, on some unintelligible dogma or article of an old-fashioned creed. Half the wars and fightings, martyrdoms, persecutions, feuds, antipathies, heartburnings in the world have been about some distinction, 'some trick not worth an egg'—so ready are mankind to sacrifice their all to a mere name!
Nathalie Vienne-Guerrin, Shakespeare's Insults: A Pragmatic Dictionary
(London: Bloomsbury, 2016), p. 171:
egg (A) Something small and worthless. 'Not worth an egg(shell)' is proverbial (Tilley, E95, see Cor 4.4.21: 'Some trick not worth an egg'). The egg is 'Shakespeare's frequent measure of insignificance' (Holland, Cor, 332).