If you Google this proverb, you’ll come up with plenty of sites that attribute it to Mark Twain (Goodreads, for one); however, I haven’t been able to find any reliable proof that he actually said it. And while I’d like to be able to say that it’s his quote (there’s something emotionally satisfying about quoting Mark Twain), I like to at least try to use accurate quotes and attributions.
What I did find is articles about how often Mark Twain is misquoted. There’s a whole website called Unquotable: Mark Twain, dedicated humorously to making up quotes that people will believe are his (not very helpful but interesting). The best actual research I found was compiled in a Huffington Post article called “That’s What He Said: Quoting Mark Twain.” The article lists various resources for checking whether the line you’re using was actually written by or said by Mark Twain. Some even let you search his letters and written works.
Well, I searched through those for this quote, and it was not in there. I looked through their lists of quotes by topic, and it still wasn’t there. I even did a Google Book search (a good way to verify quotes by writers, by the way), and none of the books that came up were his (or even that old). One of them, The Dictionary of Modern Proverbs, happens to be on my bookshelf (I guess I should’ve started there), and although it traces the line back to several variations and sources, none of those sources are Mark Twain.
Of course, at this point, the idea that Mark Twain said this is so firmly entrenched in the internet that there’s no changing it, true or false. Which is also kind of funny in context with the quote, isn’t it?