The four sons of Horus were a group of four gods in Egyptian religion, who were essentially the personifications of the four canopic jars, which accompanied mummified bodies. Since the heart was thought to embody the soul, it was left inside the body. The brain was thought only to be the origin of mucus, so it was reduced to liquid, removed with metal hooks, and discarded. This left the stomach, liver, large intestines, and lungs, which were removed, embalmed and stored, each organ in its own jar. There were times when embalmers deviated from this scheme: during the 21st Dynasty they embalmed and wrapped the viscera and returned them to the body, while the Canopic jars remained empty symbols.