What is "hypocephalus"

A hypocephalus is a small disk-shaped object generally made of stuccoed linen, but also of papyrus, bronze, gold, wood, or clay, which ancient Egyptians from the Late Period onwards placed under the heads of their dead. The circle was believed to magically protect the deceased, cause the head and body to be enveloped in light and warmth, making the deceased divine. It replaced the earlier cow-amulet.