Sage Agastya and Sage Vasistha, are considered, two of the Greatest Sages, ever lived in India. They both are also the part of the Saptarishis – [ the seven great rishis ] and received there vast wisdom directly from Lord Dakshinamurty who is considered as Adi Guru.
They where both mythical and historical figures and lived in India at certain point of time. While Sage Vasistha ashrams are found in North India , Sage Agastya as per both history and mythology crossed the Vindya mountains and came to South India . He is considered as the father of Tamil language. It is said that by bathing in the holy tank of Agastya on the southern side, one acquires a knowledge of several languages. Agastya bathes in it in the company of sages in the month of Bhadrapada and worships Arunadri.
Sage Vasistha was also a royal sage who was said as the Guru of Suryavansa [the Solar Dynasty] where Lord Rama was incarnated . Sage Vasistha advised Lord Rama, and took him to the path of liberation, by his wiseness . His conversation with Lord Rama, and instruction to Lord Rama, later become a principle text on understanding the secret meaning of Vedas. The Yoga Vasistha , is similar to what Bhagvad Gita was to Mahabharata, where the principle philosophy of Mahabharata was expressed which is authored by Sage Vyasa with the help of Lord Ganesha. Similarly “Yoga Vasistha “ which is considered as Maharamayana written by Sage Valmiki, on the request of Lord Brahma, who is also the writer for the original Ramayana. By bathing in the holy tank of Vasishta on the northern side, one understands the meaning of the Vedas. Vasishta comes here from Mount Meru in the month of Asvija and, after bathing in it, meditates upon the Lord of Sona.