Take Greek pitch and wax, and dissolve them in a clay vessel. And these things having been dissolved, let a small drop of galbanum be added, [and] let them cook for a long time, stirring with a spatula. Likewise, take mastic, frankincense, and gum arabic, and let them be mixed with the rest. Having done this, let it be removed from the fire, and when it is lukewarm let her smear her face; but let her take care [not to touch] the eyebrows. Let her leave it on for an hour until it becomes cold. Then let her remove it. This refines the skin and makes the face beautiful, and it removes the hairs and renders every blemish well colored and clear.”
This could actually work as a depiliatory, but you're probably safer to stick with a modern, commercially available one. You would have to get the proportions just right or you'd end up with either (1) a gooey, sticky mess or (2) a concoction that would harden too fast and be painful to remove.
The wax is probably beeswax. Galbanum, mastic, frankincense, and gum arabic are all resins that come from trees; they are often used as incense. Greek pitch is also a tree-based resin, used historically to (among other things) weather-proof wood. It is dark and sticky, somewhat like molasses. This mixture would look very odd on a person's face.
Source: The Trotula, 12th century