This symbol was created by John Dee and described in the Monas Hieroglyphica, or Hieroglyphic Monad, in 1564. The symbol is intended to represent the reality of the monad, a singular entity from which all material things are said to derive.
The image here includes graph lines to illustrate the specific proportions described by Dee in which writings.
Summary of the Hieroglyphic MonadDee summarized his description of the glyph as such: "The Sun and the Moon of this Monad desire that the Elements in which the tenth proportion will flower, shall be separated, and this is done by the application of Fire."
The symbol is constructed from four distinct symbols: the astrological signs for the moon and the sun, the cross, and the zodiacal sign of Aries the ram, represented by the two semi-circles at the bottom of the glyph.
For the full article, please check out John Dee's Hieroglyphic Monad.