Sage Agasthya is mentioned in the Rig Veda : in fact he authored hymns 166-190.

He is also mentioned in Tamil Literature, Sangam as well as later works in Tamil.

Star Canopus, Agasthya.

He is credited with the firs grammar book in Tamil,Agathiyam, which was followed by Tholkappiyar later by about 300 years(there is some discussion on this).

The Agastya mentioned in Tamil has been dated somewhere around 3000-5000 BC.

On the other hand, the Agasthya mentioned in the Vedas, Puranas ,Ramayana and Mahabharata is dated earlier.

Agasthya was the one who taught the Adhitya Hrudaya stotra to Lord Rama in the battle field .

Mahabharata recounts the story of Agasthya, Ilvala and Vatapi:Vatapi was swallowed by Agasthya.

Tamil literature says that he was entrusted with the task of spreading Tamil by Lord Shiva who is believed  to have founded Tamil and Shiva was the Chief of the First Tamil…