The basic symbol for plurality among  ancient Kemet was the number 3: even the way they wrote the word for "plurality" in hieroglyphics consisted of three vertical marks ( | | | ).  Triads of deities were also used in Kemet way of life to signify a complete system. Examples include references to the God Atum "when he was 1 and became when he gave birth ton Shu and Tefnut, and the triad of Horus, Osiris, and Isis.

Just a few examples of the 3 & 9 in Kemet

 The second God, Re, named three times to define the sun: dawn, noon, and evening.
 Thoth is described as the œthrice-great god of wisdom?
 A doomed prince was doomed to three fates:to die by a crocodile, a serpent, or a dog.
 Three groups of three attempts each (nine attempts) were required for a legendary peasant to recover his stolen goods.
 A boasting mage claimed to be able to cast a great darkness to last three days.
 After asking Thot for help, a King of Ethiopia was brought to Thebes and publicly beaten three further times.
 An Ethiopian mage tried” and failed” three times to defeat the greatest mage of Egypt.
 An Egyptian mage, in an attempt to enter the land of the dead, threw a certain powder on a fire three times.
 There are twelve (three times four) sections of the Egyptian land of the dead. The dead disembark at the third.
 The Knot of Isis, representing life, has three loops.

Goddess Maat in hieroglyphs

Maat was the Goddess of harmony, justice, and truth represented as a young woman, sitting or standing, holding , the symbol of power, in one hand and an Ankh, the symbol of eternal life, in the other. Sometimes she is depicted with wings on each arm or as a woman with an ostrich feather on her head. Depictions of Maat as a Goddess are recorded from old Kingdoms.
A section of the Kemet Book of the Dead written on papyrus showing the "Weighing of the Heart" in the Duat using the feather of Maat as the measure in balance.