There is much to say of Horus/Ra , this is one interesting aspect :
The Eye of Horus was believed to have healing and protective power, and it was used as a protective amulet. It was also used as a notation of measurement, particularly for measuring the ingredients in medicines and pigments. The symbol was divided into six parts, representing the shattering of Horus´ eye into six pieces. Each piece was associated with one of the six senses and a specific fraction.
More complex fractions were created by adding the symbols together. It is interesting to note that if the pieces are added together the total is 63/64 not 1. Some suggest that the remaining 1/64 represents the magic used by Thoth to restore the eye, while others consider that the missing piece represented the fact that perfection was not possible. However, it is equally likely that they appreciated the simplicity of the system which allowed them to deal with common fractions quickly, after all they already had a symbol for the number “1” and they had other numerical notations available when they needed to use smaller fractions.
edit , added :
More on Horus :
from a site with a good description :
The Wadjet (or Ujat, meaning “Whole One”) is a powerful symbol of protection in ancient Egypt also known as the “Eye of Horus” and the “all seeing eye”. The symbol was frequently used in jewellery made of gold, silver, lapis, wood, porcelain, and carnelian, to ensure the safety and health of the bearer and provide wisdom and prosperity. However, it was also known as the “Eye of Ra”, a powerful destructive force linked with the fierce heat of the sun which was described as the “Daughter of Ra”. The “eye” was personified as the goddess Wadjet and associated with a number of other gods and goddesses (notably Hathor, Bast, Sekhmet, Tefnut, Nekhbet and Mut).
The Eye of Horus
Horus was an ancient a sky god whose eyes were said to be the sun and the moon. However, he soon became strongly associated with the sun (and the sun god Ra as Ra-Horakhty (“Ra, who is Horus of the two horizons”) while Thoth was associated with the moon. An ancient myth describes a battle between Horus and Set in which Horus´ right eye was torn out and Set lost his testicles! Thoth magically restored Horus´ eye, at which point it was given the name “Wadjet” (“whole” or “healthy”). In this myth it is specifically stated that it is Horus´ left eye which has been torn out, so the myth relates to the waxing and waning of the moon during which the moon appears to have been torn out of the sky before being restored once every lunar month.
There are a number of depictions of the restoration of the eye in Greco-Roman temples. Thoth is assisted by fourteen gods including the gods of the Ennead of Hermopolis or thirty male deities (in Ismant el-Kharab, the Dakhla Oasis). Each god represented one of the fifteen days leading up to the full moon, and to the waning moon. The restored eye became emblematic of the re-establishment of order from chaos, thus closely associating it with the idea of Ma´at. In one myth Horus made a gift of the eye to Osiris to help him rule the netherworld. Osiris ate the eye and was restored to life. As a result, it became a symbol of life and resurrection. Offerings are sometimes called “the Eye of Horus” because it was thought that the goods offered became divine when presented to a god.
According to later traditions, the right eye represented the sun and so is called the “Eye of Ra” while the left represented the moon and was known as the “eye of Horus” (although it was also associated with Thoth). However, in many cases it is not clear whether it is the left or right eye which is referred to. Others myths suggest that it is Horus’ right eye which was torn out and that the myth refers to a solar eclipse in which the sun is momentarily blotted from the sky.
The Eye of Ra
According to one myth, Ra (who was at that point the actual Pharaoh of Egypt) was becoming old and weak and the people no longer respected him or his rule. They broke the laws and made jokes at his expense. He did not react well to this and decided to punish mankind by sending an aspect of his daughter, the Eye of Ra. He plucked her from the Ureas (royal serpent) on his brow, and sent her to earth in the form of a lion. She waged war on humanity slaughtering thousands until the fields were awash with human blood. When Ra saw the extent of the devestation he relented and called his daughter back to his side, fearing that she would kill everyone. However, she was in a blood lust and ignored his pleas. So he arranged for 7,000 jugs of beer and pomegranate juice (which stained the beer blood red) to be poured all over the fields around her. She gorged on the “blood” and became so drunk that she slept for three days and awoke with a terrible hangover. Thus mankind was saved from her terrible vengeance.
There are a number of different versions of the myth, and a number of goddesses are given the title “Eye of Ra”, in particular Hathor, Sekhmet, Tefnut, Bast, Mut, Nekhbet and Wadjet . The “Daughter of Ra” was sometimes symbolised as a Cat who protected Ra from the serpent Apep (linking it with the leonine aspects of Hathor, Bast, Sekhmet, Tefnut, Mut, Nekhbet and Wadjet amongst others). The Cat was also thought to be able to cure and scorpion or snake bite and was associated with the goddesses Isis (although she is only linked to the symbol in its protective function)