Indian classical music is the art music of the Indian subcontinent. The origins of Indian classical music can be found in the Vedas, which are the oldest scriptures in the Hindu tradition dating back to 1500 BCE. The Samaveda was derived from the Rigveda so that its hymns could be sung as Samagana. These hymns were sung by Udgatar priests at sacrifices in which the Soma ritual drink, clarified and mixed with milk and other ingredients, was offered in libation to various deities. This chanting style evolved into jatis and eventually into ragas. Indian classical music has also been significantly influenced by, or syncretised with, Indian folk music. Bharat's Natyashastra was the first treatise laying down fundamental principles of dance, music, and drama.