(Latin) "first matter," from Greek prōtē hylē.
In alchemy, the base of all things, and thus the origin of all things.
"As all things were from one..." —Hermes, The Emerald Tablet
The basis of alchemy is to reduce imperfect elements to that original source, from which one can transmuted into something better.
"Each thing can be disarranged within its own elements. With the help of heat, we can disarrange ice into water, because water is the element of ice. Therefore, all the metals of the Earth can be disarranged into Mercury, because Mercury is the prima materia of all the metals. The human being can be disarranged in the semen, because this is the element that he emerged from. Each thing can be disarranged to the elements of which it is composed." —Samael Aun Weor, Kabbalah of the Mayan Mysteries