From The Little, Brown Book of Anecdotes, ed. Clifton Fadiman:

(1) To Queen Christina Descartes tried to explain his mechanistic philosophy: the view that all animals are mechanisms. The queen countered this by remarking that she had never seen a watch give birth to baby watches.

(As a gloss on this anecdote, the General Editor offers his clerihew:

Said Descartes, “I extoll

Myself because I have a soul

And beasts do not.” Of course

He had to put Descartes before the horse.)

(2) Descartes’s coordinate system was one of his main contributions to the development of mathematics. It is said that the idea came to him during a period of idleness in his military service as he lay on his bed watching a fly hovering in the air. He realized that the fly’s position at every moment could be described by locating its distance from three intersecting lines (axes). This insight was the basis of Cartesian coordinates.

(3) Descartes once constructed a robot in the form of a girl, which he later had occasion to transport by sea. The ship’s captain, out of curiosity, looked into the chest in which the robot was packed and was horrified by the lifelike form, which moved like an animated being. Thinking that this could only be the devil in disguise, he threw the chest and its contents into the sea.