Any two conjugate diameters of an hyperbola are harmonic conjugates with regard to the asymptotes.
Encyclopaedia Britannica (New York: The Encyclopaedia Britannica Company, 1910) 11:700
2400×2303, 268.3 KiB
1024×982, 45.4 KiB
640×614, 25.9 KiB
320×307, 11.7 KiB