René Descartes was a French man who lived in the 1600s. When he was a child, he was often sick, so the teachers at his boarding school let him stay in bed until noon. He went on staying in bed until noon for almost all his life. While in bed, Descartes thought about math and philosophy.
One day, Descartes noticed a fly crawling around on the ceiling. He watched the fly for a long time. He wanted to know how to tell someone else where the fly was. Finally he realized that he could describe the position of the fly by its distance from the walls of the room. When he got out of bed, Descartes wrote down what he had discovered. Then he tried describing the positions of points, the same way he described the position of the fly. Descartes had invented the coordinate plane! In fact, the coordinate plane is sometimes called the Cartesian plane, in his honor.
This website, quoted above, claims that René Descartes created his coordinate system by watching a fly on his bedroom ceiling while sick in bed. I've found the same claim on several other sites, including this one and this one which says "legend has it." This claim seems a bit absurd, as this website and this website place Descartes between ages 8 and 18 at the time of his discovery. The closest thing I've found to a reputable source is this page from Southern Arkansas University.
Is there an academic source confirming or disconfirming this claim?