This tradition was once practiced all over India. However the Muslim subjugation of north India restricted Shaiva Siddhanta to the south, where it merged with the Tamil Saiva movement expressed in the bhakti poetry of the Nayanars. It is in this historical context that Shaiva Siddhanta is commonly considered a "southern" tradition, one that is still very much alive. The Tamil compendium of devotional songs known as Tirumurai, the Shaiva Agamas and "Meykanda" or "Siddhanta" Shastras, form the scriptural canon of Tamil Shaiva Siddhanta.