File:Alchemy fire symbol.svg

The triangle is an ancient Egyptian emblem of the Godhead, and also a Pythagorean symbol for wisdom. In Christianity it is looked upon as the sign of the triple personality of God. Again, in distinction from the next sign, it is another sign for the female element, which is firmly based upon terrestrial matters, and yet yearns after higher things. The female is always earthly in its conception.

— Rudolph Koch, The Book of Signs (p3)