The oldest source of incense is the Vedas, specifically, the Atharva-veda and the Rigged in India. There, incense-burning was used both to create pleasing aromas and as a medicinal tool. Its use in medicine is considered the first phase of Ayurveda, which uses incense as an approach to healing. Incense-making was thus almost exclusively done by monks.
The specific knowledge of incense as a healing tool was assimilated into the religious practices of the time - early Hinduism. As Hinduism matured and Buddhism was founded in India, incense became an integral part of Buddhism as well. Around 200 AD, a group of wandering Buddhist monks introduced incense-making to China.
In accordance with Ayurvedic principles, the ingredients that go into incense-making may be categorized into five classes: ether (fruits) such as star anise; water (stems and branches), such as sandalwood, aloeswood, cedar wood, cassia, frankincense, myrrh, and borneol; earth (roots), such as turmeric, vetiver, ginger, costus root, valerian, Indian spikenard; fire (flowers), such as clove; and air (leaves), like patchouli.