Complex sentence: The best-known example of a mask is probably the death mask of K'inich Janaab' Pakal, ruler of Palenque; it had a "skin" made from jade and "eyes" made from mother-of-pearl and obsidian.
Split into simpler sentences: The best-known example is probably the death mask of K'inich Janaab' Pakal, ruler of Palenque. A life-size mask created for his corpse had "skin" made from jade and "eyes" made from mother-of-pearl and obsidian.