In an Italian museum (probably the Leonardo da Vinci Museum in Florence) I saw a compass for drawing arbitrary conical sections. I believe the legend mentioned only ellipses, but it could in principle draw the others too; I think it was invented.

The basic principle is that the "central" arm (in general, the focal arm) of the compass is held at a fixed (per drawing) angle to the desk, while the pencil arm adjusts in length (so that it is shorter at the perigee and longer at the apogee).

In an Italian museum (probably the Leonardo da Vinci Museum in Florence) I saw a compass for drawing arbitrary conical sections. I believe the legend mentioned only ellipses, but it could in principle draw the others too.

The basic principle is that the "central" arm (in general, the focal arm) of the compass is held at a fixed (per drawing) angle to the desk, while the pencil arm adjusts in length (so that it is shorter at the perigee and longer at the apogee).