Early Indian epigraphy

The earliest traces of epigraphy in the Indian Subcontinent are found in the undeciphered inscriptions of the Indus Valley Civilization (Indus script), which date back to the early 3rd millennium BC. Two other important archeological classes of symbols are found from the 1st millennium BCE, Megalithic Graffiti Symbols and symbols on punch-marked coins, though most scholars do not consider these to constitute fully linguistic scripts, and their semiotic functions are not well understood. The earliest deciphered epigraphic inscriptions of significant length are the Edicts of Ashoka of the 3rd century BCE, written in forms of Prakrit in the Brahmi script. Jain inscriptions in South India written in Tamil-Brahmi, Bhattiprolu alphabet and the Kadamba alphabet are also of relatively early date. Short Brahmi inscriptions on potsherds from the 4th century BCE have been reported from the ruins of Anuradhapura and are the only pre-Ashokan examples of Brahmi that have received any scholarly acceptance, though reports have appeared in the Indian press claiming potsherd inscriptions from an even earlier period (6th to 4th century BCE).

Writing in Sanskrit (Epigraphical Hybrid Sanskrit, EHS) appears only later, in the first to fourth centuries CE.

Indian epigraphy becomes more widespread over the 1st millennium, engraved on the faces of cliffs, on pillars, on tablets of stone, drawn in caves and on rocks, some gouged into the bedrock. Later they were also inscribed on palm leaves, coins, Indian copper plate inscriptions, and on temple walls.

...
Wikipedia