Mother letters assinged to pillars?

Abrac

Does anyone know if Aleph, Mem, and Shin are typically assigned to the Central Pillar, the Pillar of Severity, and the Pillar of Mercy respectively? I read it here: https://en.wikipedia.org/wiki/Sephirot, toward the bottom, under the heading "Associations of the 3 columns." I've never heard that before, but I'm not that educated in the finer points of Kabbalah. Was wondering if it's common or well-known and if it was used in the Golden Dawn.
 

Aeon418

Any system that uses the Sepher Yetzirah as a foundation text uses the attribution of the three Mother Letters and their associated elemental attributions. This doctrine is derived from the SY 2:1.

William Wynn Westcott said:
The twenty-two sounds and letters are the Foundation of all things. Three mothers, seven doubles and twelve simples. The Three Mothers are Aleph, Mem, Shin, they are Air, Water and Fire. Water is silent, Fire is sibilant, and Air derived from the Spirit is as the tongue of a balance standing between these contraries which are in equilibrium, reconciling and mediating between them.
Aryeh Kaplan said:
Twenty-two Foundation Letters:
Three Mothers
Seven Doubles
and Twelve Elementals.
The Three Mothers are Alef Mem Shin,
Their foundation is
a pan of merit
a pan of liability
and the tongue of decree deciding between them.
[Three Mothers, Alef Mem Shin
Mem hums, Shin hisses
and Alef is the breath of air
deciding between them.
As you might expect there is some disagreement over the attributions. Aleph/Air is almost universally assigned to the Middle Pillar. The Golden Dawn system is the same as the Wiki article you linked to. Aryeh Kaplan reverses the attribution of Mem and Shin due to his desire to conform certain technical details to those found in the the Zohar.
 

Abrac

Think I found what I was looking for. This page, http://www.hermetics.org/gd/GD-5.html, near the bottom, shows a diagram from the GD Fifth Knowledge Lecture. Fire is in Chokmah and Water in Binah. As the elements are reflected down the Tree, Fire reflects diagonally into Geburah; likewise Water is reflected into Chesed and so on down the Tree. Air is in Kether and is reflected straight downward. This seems to be customary in the GD as it's found in several other places throughout their teachings.

Waite seems to have followed this, in the FRC at least.

"It represents Shekinah as the Lady of Reconciliation and Lady of the Pillar of Benignity, intermingling and reconciling the influences of Chesed and Geburah, regarded as cleansing water and saving fire."​

As I understand it, "cleansing water and saving fire" should be taken as "respectively." The next quote makes it pretty clear.

"Fire of purgation in Geburah; holy Fire of judgment. In the name of transmuting Fire."​

"There is a Water of the wise in Chesed. There is a Fire in the Water of the wise. That Sacred Fire is an influx from Chokmah. . ."​

This last quote appears to be describing Water in Chesed which receives an influx of Fire from Chokmah through the path that connects them.