mundane ends like childbirth, these sexual yogas were associated with the movement of subtle body energies (like Kundalini and Chandali, which were also seen as goddesses), and also with spiritual ends. These practices seemed to have developed at around the same time in both Saiva and Buddhist circles, and are associated with figures such as Tirumülar, Gorakhnath, Virupa, Naropa. The tantric mahasiddhas developed yogic systems with subtle body and sexual elements which could lead to magical powers (siddhis), immortality, as well as spiritual liberation (moksha, nirvana). Sexual yoga was seen as one way of producing a blissful expansion of consciousness that could lead to liberation. According to Jacob Dalton, ritualized sexual yoga (along with the sexual elements of the tantric initiation ritual, like the consumption of sexual fluids) first appears in Buddhist works called Mahayoga tantras (which include the Guhyagarbha and Guhyasamaja). These texts "focused on the body's interior, on the anatomical details of the male and female sexual organs and the pleasure generated through sexual union." In these texts, sexual energy was also seen as a powerful force that could be harnessed for spiritual practice and according to Samuel "perhaps create the state of bliss and loss of personal identity which is homologised with liberating insight." These sexual yogas continued to develop further into more complex systems which are found in texts dating from about the ninth or tenth century, including the Saiva Kaulajñānanirṇaya and Kubjikātantra as well as the Buddhist Hevajra, and Cakrasamvara tantras which make use of charnel ground symbolism and fierce goddesses. Samuel writes that these later texts also combine the sexual yoga with a system of controlling the energies of the subtle body. There is considerable evidence that the Hevajra and Cakrasamvara tantras borrow significant portions from Saiva sources. The text Cakrasamvara and its commentaries have revealed numerous attempts by the Buddhists to enlarge and modify it, both to remove references to Saiva deities and to add more Buddhist technical terminology. Tantric Age From the 8th to the 14th century, Tantric traditions rose to prominence and flourished throughout India and beyond. By the 10th century, the main elements of tantric practice had reached maturity and were being practiced in Saiva and Buddhist contexts. This period has been referred to as the 'Tantric Age' by some scholars due to prevalence of Tantra. Also by the 10th century, numerous tantric texts (variously called Agamas, Samhitas and Tantras)