I was reading "Venice: A Traveller's Reader" by John Julius Norwich and found an early mention of something like a guillotine from 1646. This excerpt is from the diary of John Evelyn. "The next day I saw a wretch executed who had murther'd his master, for which he had his head chop'd off by an axe that slid down a frame of timber, between the two tall columns in St. Mark's Plaza at the sea brink; the executioner striking on the axe with a beatle, and so the head fell off the block."