I Have Never Let My Schooling

This quip is misattributed to Twain. Quote Investigator credits it to the British writer Grant Allen, who published variants of this exact sentiment in at least four of his works between 1894 and 1899. The first link to Twain appeared in a 1907 Daisy Air Rifle advertisement. Ironically, Twain's own recorded views on self-education were more cautious: in the posthumously published essay "Taming the Bicycle," he warned that the self-taught man "seldom knows anything accurately."