"Close your eyes, and from your own consciousness of perception try and think outward to the extremist 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."

- Madam Blavatsky, The Secret Doctrine