An easy project for your grandchildren

[John Hasler]

Now this brought to my mind one of my interesting "pillow problems" (problems which generally aren't solved but help me to fall asleep): would it be possible, on a lathe, to turn an ellipsoid rather than a sphere? Uhmmm…

Use the principle of the trammel of Archimedes.
https://www.youtube.com/watch?v=Hfw0yYur5S4