1961 August 17,New Scientist, volume 11, number 248, Reed Business Information, ISSN0262-4079, page 413:
In his Mantissa Plantarum (1767) and Mantissa Plantarum altera (1771), [Linnaeus] regularly used ♂, ♀ and ☿ for male, female and hermaphrodite flowers respectively.
2012,Olga B. A. van den Akker,Reproductive Health Psychology, John Wiley & Sons, ISBN 9781119967477, page 40:
The genders are typically represented by symbols derived from the planets. The female (Venus) and male (Mars) symbols (shown below) are commonly known and used.
Venus ♀ Mars ♂ Mercury ☿
As not everyone believes that they fit into either the male or female gender role regardless of their biological genetic sex, they tend to refer to themselves as the third category, intersex, intergender or transgender (see Mercury symbol above).