Close your eyes, and from your own consciousness of perception try and think outward to the extremest limits in every direction. You will find that equal lines or rays of perception extend out evenly in all directions, so that the utmost effort of perception will terminate in the vault of a sphere. The limitation of this sphere will, of necessity, be a great Circle, and the direct rays of thought in any and every direction must be right line radii of the circle. This, then, must be, humanly speaking, the extremest all-embracing conception of the Ain-Soph manifest, which formulates itself as a geometrical figure, viz., of a circle, with its elements of curved circumference and right line diameter divided into radii. Hence, a geometrical shape is the first recognisable means of connection between the Ain-Soph and the intelligence of man.
— The Secret Doctrine, 1:429