The Umachal rock inscription is the earliest epigraphic source discovered in Assam. Dated to the 5th century, the rock description was discovered in the north-eastern slopes of the Nilachal Hills (called Umachal), near Guwahati city. The artifact is dated primarily on the basis of the identification of the named Surendra Varman with Mahendra Varman (fl. c470-494) of the Varman dynasty. The script is in the eastern variety of the Gupta script and the language is Sanskrit prose. Though the Nilachal Hills is known for the Kamakhya Temple, a shakta/tantra site, this temple was for Balabhadra, a god of the Vaishnavite pantheon.
Another inscription, the Nagajari-Khanikargaon rock inscription, though undated, is sometimes claimed as the earliest on stylistic grounds.
Translation
"This cave (-temple) of the illustrious Lord Balabhadra has been constructed by Maharajadhiraja Sri Surendra Varman."