Budh is a prototype of gender roles. In Hindu Astrology, Budh is the planet Mercury. Briahspati cursed his wife Tara when she was pregnant with Budh from her lover Chandra. Brihaspthi cursed Tara that her child Budh will neither be born as female nor male.
Budh married Ila who was also cursed to switch genders every month as she stepped into the grove of Shiva and Parvati. As a man, Ila is known as Sudhyumna. The Linga Purana and Mahabharatha states that along with Ila, her horse also changed gender. Ila was cursed that as a female she would not remember her life as a male and vice versa.
Ila married Budh and spent a month with him to consummate the marriage. But when she woke up as Sudhyumna, he could not remember anything about Ila – who is now the wife of Budh. Budh convinced Sudhyumna and stayed with Ila for a year. Ila gave birth to the pururavas who became the king of the Lunar dynasty.
Ila sacrificed her horse to Shiva who in turn restored her masculinity permanently. The Puranas recorded the birth of Pururavars to narrate the end of Ila’s gender condition. There are certain writings that say Ila was born female, married Budh and then transformed into a male. Sudhyumna was cursed by Shiva and Parvati to be a female and then he became Ila again. In most of the versions of Mahabharatha, it is stated that Ila wants to live as a man but in Skanda Purana alone it is mentioned that she desires to be a woman.