Quaternions came from Hamilton after his really good work had been done; and, though beautifully ingenious, have been an unmixed evil to those who have touched them in any way, including Clerk Maxwell. – Lord Kelvin, 1892.
Lie at the threshold of Zeus, full of lots, one of good, the other of evil lots, and that he to whom Zeus gives a mixture of the two Sometimes meets with evil fortune, at other times with good; but that he to whom is given the cup of unmingled ill, Him wild hunger drives o'er the beauteous earth. – Plato, in "The Republic" source