Adi Shankaracharya (8th century CE) established four mathas in the four corners of India - Dwarka (west), Puri (east), Sringeri (south), and Joshimatha (north) - to unify and revitalize Hinduism. Madhavacharya and Ramanujacharya were other influential Hindu philosophers but did not establish this network. Bhaskaracharya was a mathematician.