The number nine.
One of the six parts of the writings of the Greek-speaking philosopher Plotinus (c. 204–205 – 270), each containing nine treatises, compiled by his student Porphyry (c. 234 – c. 305).
The collection of nine gods worshipped at Heliopolis and taking part in the Heliopolitan creation myth, together representing the sum of all the elements of the created world: Atum, Shu, Tefnut, Nut, Geb, Osiris, Isis, Set, and Nephthys.