"The 'Mundane Egg' is, perhaps, one of the most universally adopted symbols, highly suggestive as it is, equally in the spiritual, physiological, and cosmological sense. . . . The mystery of apparent self-generation and evolution through its own creative power repeating in miniature the process of Cosmic evolution in the egg, both being due to heat and moisture under the efflux of the unseen creative spirit, justified fully the selection of this graphic symbol. The 'Virgin Egg' is the microcosmic symbol of the macrocosmic prototype -- the 'Virgin Mother' -- Chaos or the Primeval Deep. The male Creator (under whatever name) springs forth from the Virgin female, the immaculate root fructified by the Ray. Who, if versed in astronomy and natural sciences, can fail to see its suggestiveness? Cosmos as receptive Nature is an Egg fructified -- yet left immaculate; once regarded as boundless, it could have no other representation than a spheroid. The Golden Egg was surrounded by seven natural elements (ether, fire, air, water), 'four ready, three secret'" (SD 1:65).
In Vedantic philosophy, used somewhat equivalently to sutratman, atman invested with the sukshma-sarira, as well as with the other sariras flowing forth from this and permeating and infilling them all as the thread-self.

"The 'Mundane Egg' is, perhaps, one of the most universally adopted symbols, highly suggestive as it is, equally in the spiritual, physiological, and cosmological sense. . . . The mystery of apparent self-generation and evolution through its own creative power repeating in miniature the process of Cosmic evolution in the egg, both being due to heat and moisture under the efflux of the unseen creative spirit, justified fully the selection of this graphic symbol. The 'Virgin Egg' is the microcosmic symbol of the macrocosmic prototype -- the 'Virgin Mother' -- Chaos or the Primeval Deep. The male Creator (under whatever name) springs forth from the Virgin female, the immaculate root fructified by the Ray. Who, if versed in astronomy and natural sciences, can fail to see its suggestiveness? Cosmos as receptive Nature is an Egg fructified -- yet left immaculate; once regarded as boundless, it could have no other representation than a spheroid. The Golden Egg was surrounded by seven natural elements (ether, fire, air, water), 'four ready, three secret'" (SD 1:65).
In Vedantic philosophy, used somewhat equivalently to sutratman, atman invested with the sukshma-sarira, as well as with the other sariras flowing forth from this and permeating and infilling them all as the thread-self.