Water - Mem
Air - Aleph
Fire - Shin
The three horizontal paths represent initiatic degrees - The Hebrew letters Mem (water), Aleph (air), and Shin (fire) on the Tree of Life correspond to baptisms by water, air/spirit, and fire - the three-degree system found in Gnosticism, Freemasonry, and Templar initiation.
Baptism by Water and by Spirit
"Aros the Philosopher says, that the Water or Spirit of the Stone is all in all, and is the only thing sought after, and requisite for this Work; for in it is the flying and fixed, the tingeing and tinged, the white and red, Masculine and Feminine composed together by an inseparable Composition. Lully says, the Spirit is the first principal Secret, the Water the next, from which Two things every thing receives its Nutriment, and every Tree, Srpout and Herb its Vegetation, and every Light its Illumination.
- Penotus - Alchymist’s Enchiridion