This exercise is really a clearing of the ground for laying your true spiritual foundations, and it consists in the building of a Sphere of Light.
On the work upon which you are about to embark it is not enough to involve simply the conscious mind. The whole of your being must become involved. Like the alchemy of old it is a total commitment to the Work, not a rational 'investigation' of it, that is alone able to bring it to a successful conclusion.
Identification with a basic symbol is a first step in this process and the most appropriate one is a Sphere of Light. This is a symbol of the whole of creation, it speaks to the ego and Soul as being the basic shape upon which worlds are formed, from their smallest part to their largest, from the energy sphere of the atom to the bowl or hemisphere of the night sky.
It is a personal symbol too of recollection and withdrawal, of concentration about a center. It is, if one likes, a three-dimensional magic circle or mandala in which the soul can safely rest and no harm can approach from the outside. In another sense it is a clearing and a purification of your aura and even the place for work, as in a surgery or laboratory.
However, the simple rational approach is not enough, you must also open your mystical heart to send receive pure love—for this is a mystical as well as an alchemical quest. You should feel the reality of the symbol with your heart as well as picturing it in your imagination and speculating about it mentally.