Egyptian fraction have been called "Horus-Eye fractions" after a theory (now discredited) that they were based on the parts of the Eye of Horus symbol. They were used in the Middle Kingdom in conjunction with the later notation for Egyptian fractions to subdivide a hekat, the primary ancient Egyptian volume measure for grain, bread, and other small quantities of volume, as described in the Akhmim Wooden Tablet. If any remainder was left after expressing a quantity in Eye of Horus fractions of a hekat, the remainder was written using the usual Egyptian fraction notation as multiples of a "ro", a unit equal
Four sons of Horus to say: "I have come to be your protection. I have bound your head and your limbs for you. I have smitten your enemies beneath you for you, and given you your head, eternally." Spell 148 in the Book of the Dead directly associates all four of Horus's sons, described as the four pillars of Shu and one of the four rudders of heaven, with the four cardinal points of the compass. Hapi was associated with the north. Imsety the human headed son of Horus, protected the liver of the deceased and was in turn protected by the goddess Isis.