Question

What sources do historians use in writing about the last 250 years of indian history? How were this preserved?

Answer 1

historians use bark of trees on which they write they use feathers as pen and dip them in dye to write the bark on which they write was called birch

Answer 2

They write how they lived, how do war take place, evidence, records and many documents.
These all are preserved in National Survey Of India.