Quote by Anonymous
Never try to teach a pig to sing: it wastes your time and it annoys the pig.
I have seen this attributed to George Bernard Shaw, Mark Twain, Paul Dickson and Robert Heinlein - but can't find the sources to prove where they said it (and thus at least narrow it down some).
Please suggest source details if you know: book, page, year, online article address (url), correction (different author...), etc.. Thanks.