Probably there is an imperceptible touch of something permanent that one feels instinctively to adhere to true humour, whereas wit may be the mere conversational shooting up of "smartness"—a bright feather, to be blown into space the second after it is launched...Wit seems to be counted a very poor relation to Humour....Humour is never artificial.

Mark Twain: The Complete Interviews (ed. University of Alabama Press, 2006) - ISBN: 9780817315221