both Śaivas and Buddhists, tantric practices often took place at important sacred sites (pithas) associated with fierce goddesses. Samuel writes that "we do not have a clear picture of how this network of pilgrimage sites arose." Whatever the case, it seems that it was in these ritual spaces visited by both Buddhists and Śaivas that the practice of Kaula and Anuttarayoga Tantra developed during the eighth and ninth centuries. Besides the practices outlined above, these sites also saw the practice of animal sacrifice as blood offerings to Śākta goddesses like Kamakhya. This practice is mentioned in Śākta texts like the Kālikāpurāṇa and the Yoginītantra. In some of these sites, such as Kamakhya Pitha, animal sacrifice is still widely practiced by Śāktas. Another key and innovative feature of medieval tantric systems was the development of internal yogas based on elements of the subtle body (sūkṣma śarīra). This subtle anatomy held that there were channels in the body (nadis) through which certain substances or energies (such as vayu, prana, kundalini, and shakti) flowed. These yogas involved moving these energies through the body to clear out certain knots or blockages (granthi) and to direct the energies to the central channel (avadhuti, sushumna). These yogic practices are also closely related to the practice of sexual yoga, since sexual intercourse was seen as being involved in the stimulation of the flow of these energies. Samuel thinks that these subtle body practices may have been influenced by Chinese Daoist practices. One of the earliest mentions of sexual yoga practice is in the Buddhist Mahāyānasūtrālamkāra of Asanga (c. 5th century), which states "Supreme self-control is achieved in the reversal of sexual intercourse in the blissful Buddha-poise and the untrammelled vision of one's spouse." According to David Snellgrove, the text's mention of a 'reversal of sexual intercourse' might indicate the practice of withholding ejaculation. Snellgrove states that it is possible that sexual yoga was already being practiced in Buddhist circles at this time, and that Asanga saw it as a valid practice. Likewise, Samuel thinks that there is a possibility that sexual yoga existed in the fourth or fifth centuries (though not in the same transgressive tantric contexts where it was later practiced). It is only in the seventh and eighth centuries however that we find substantial evidence for these sexual yogas. Unlike previous Upanishadic sexual rituals however, which seem to have been associated with Vedic sacrifice and