The Solitary Ray is the Pythagorean Monad. It strides through the Seven Regions of the Universe in three steps:
First Logos, The One. Second Logos, The One made Three, concreting into Third Logos, where the Three live within The One, thus making up the Perfect Square in heaven — and a Cube on earth. Terrestrial number 2 is useless and unlucky.
Twin serpents conceal the One from the many.
The Seven Rays of Logos, 3 + 4, are Three Principles + Four Vehicles on the material plane. They vivify Seven Worlds of Being, symbolised by the Ladder, as follows: Absolute, Archetypal, Spiritual, Manasic, Psychic, Astral, and Elemental. The Earth is no World.