Generally the seeing of light during meditation is a favourable sign of present experience or good omen of future experience. It indicates that meditation in depth is being attained, or will be later. The light may seem spread out in space or as a thin ray alone. It may appear as a tiny black-centered sun or as a large round ball. There are still other forms--such as lightning and stars. Generally, too, there will be a living dynamic quality in it, a movement, a winking, and a fiery flickering.
-- Notebooks Category 22: Inspiration and the Overself > Chapter 4: Introduction To Mystical Glimpses > # 163