The ancient Indians knew writing at least as early as 2500 BC, but no manuscripts older than the 4th century arc available. The manuscripts were written on birch bark and palm leaves, but in Central Asia, where Prakrit had gone from India, manuscripts were also written on sheep leather and wooden tablets.
The Vedas and related books were put into writing quite late. The Rig Veda describes the period 1500-1000 bc, and the later Vedic literature gives glimpses of the history of about 1000-600 bc.
Buddhist literature, the two epics, Ramayana and Mahabharata, and other books help us to know about the subsequent periods. We mainly rely on literary sources for the history of India just before the Mauryas.
Later, literary sources began to supplement other sources. The Puranas are regarded by some as having been written historically, though this view is disputed by other scholars.
However, generally the first 'historical' writing by an Indian is attributed to Kalhana who wrote the Rajatarangini in the twelfth century, giving a dynastic chronicle of the kings of Kashmir.
Some important ancient works that are important source materials include Asvaghosa's Buddhacharita (ad 100) in Pali, the Gaudavaho in Prakrit by Bappaira which talks of King Yasovarman (ad 750), and the Harshacharita by Bana which is an account on the life of King Harsha (ad 606-47).
The Sangam literature gives an insight into the social, economic and political life of the people of deltaic Tamil Nadu in the early Christian centuries. Its information regarding trade and commerce of the time is attested to by foreign accounts and archaeological finds.