The propagation of linga worship on a large scale in South India is believed to be from Chola times (late 7th century A.D.), through Rig veda, the oldest literature details about worshipping Shiva in the form of linga. Pallavas propagated Somaskanda as the principal form of worship, slightly deviating from the Shaiva agamas; Cholas being strict shaivas, established lingams in all the temples.