The Rajatarangini ( “The River of Kings”) was written in Sanskrit by Kashmiri historian Kalhana in the 12thcentury. The Rajatarangini ( “The River of Kings”) is a metrical historical chronicle of north-western Indian subcontinent. Book provides precious information about early Kashmir and its neighbors in the north western parts of the Indian subcontinent.
For more info check wiki link: https://en.wikipedia.org/wiki/Rajatarangini