It always amazes me that besides the Cartesian plane, Descartes was also the person who introduced the basic form of (Re) +(Im)i for complex numbers and yet never thought to plot this on his plane. It was Wallis (1685) nearly 50 years later that suggested it and then the idea only got traction once Gauss liked the work of Argand in 1831.
[I tell my students who miss a connection between two ideas, that even some of the greats, like Descartes, missed a connection.]