Device developed by Jacques de Vaucanson and first exhibited in 1738. An attempt to reproduce life artificially, which gained widespread public attention. The device is based on the belief of the time that man was an advanced mechanism resembling an mechanism of weights, motors and wheel-work.
The actual duck can hardly be explained with words.
Seeing the drawings of the duck for the first time* made me question my views of strong AI, as it now illustrates how much the metaphors whe use to explain life changes. At Vaucansons time, the industrial age, the machine was the popular metaphor to look at man through, today it is the computer. In ancient greece, man was believed to be made out of clay and given life by a divine presence. I don't believe the view of the brain as a pure logical device will seem less silly in later times than the other ways of looking at man do today.
* Actually, this didn't happen the first time I saw it, but the second. The first time I saw it I had a bad hangover, and accidentally dropped by it in the Norwegian magazine of popular science Vissenskaft Illuschtrert, which presented it as "the duck that could both eat and shit". I couldn't stop laughing for the rest of that day.