One of my favorite mathematical diagrams: http://www-math.mit.edu/~andyp/Figures/FIGURE2.pdf http://www-math.mit.edu/~andyp/Figures/FIGURE2.pdf, from Matveev, F

One of my favorite mathematical diagrams: http://www-math.mit.edu/~andyp/Figures/FIGURE2.pdf http://www-math.mit.edu/~andyp/Figures/FIGURE2.pdf, from Matveev, Fomenko, Algorithmic and computer methods in three-dimensional topology.