If one forgets the bottom “legs”, it is precisely the sign of the hermetic mercury: the moon (aka silver), the sun (gold) and the cross or quaternary of elements.

Why the legs? Because, as Dr. Dee himself explains in Theorem X, it is the seal of Aries, i.e. Fire, and it shows that nothing can be done without it.It is not by chance that one of the names used by the adept of the Art has always been Philosophers by Fire.

Best

A.M.