Thirumoolar, in his Thirumantiram, talks of sages who worshipped Lord Siva, said R. Narayanan in a discourse. He mentions four sages — Sanaka, Sanatana, Sanandana and Sanatkumara. He mentions four others, too, who also became spiritual gurus. These four are Sivayoga muni, Vyagrapada, Patanajali, and Thirumoolar himself.
Thirumoolar was originally Sundaranatha. When a cowherd called Moolan died, Sundaranatha exited his body and entered Moolan’s body and became Thirumoolar, the saint. Thirumoolar acknowledges that all this happened because Lord Siva wanted Vedanta and the knowledge of the Agamas to reach everyone. Thirumoolar had seven disciples, and he gives their names — Malankan, Indiran, Soman, Brahman, Rudran, Kalangi and Kanjamalayan. Thirumoolar’s teachings were carried down from generation to generation. This is seen from one of Thayumanavar’s statements.
Thayumanavar’s guru was Mauna guru, and Thayumanavar says that Mauna guru followed the tradition of Thirumoolar. Thayumanavar lived in the 18th century. So clearly, Thirumoolar’s teachings had an impact that continued to extend for centuries, and the impact still continues. Thirumoolar says that Sanaka, Sanatana, Sanandana and Sanatkumara learnt about the greatness of Lord Siva, and they wanted to communicate it to everyone because they wanted everyone to have the joyful experience they had had. It is not enough if we have jnana. Imparting knowledge to others is important. Thirumoolar says Lord Siva has no desires. He is not subject to temptations. His good qualities are limitless, and cannot be described. He does not show His greatness to everyone. He reveals it only to a few. Thirumoolar again repeats the names of the sages who had this blessing.