The most authentic source of Mauryan history is the epigraphical evidence.
The edicts of Ashoka are the oldest, the best preserved and the most
precisely dated epigraphic records of India. The inscriptions are engraved
on rocks, boulders, cave walls and pillars of stone. The inscriptions of
Ashoka are of two kinds -the smaller group consists of declaration of the
king as a lay Buddhist to his church. These describe his own acceptance of
Buddhism and his relationship with the Samgha. The second group of
important inscriptions consists of Major and Minor rock edicts and the
pillar edicts.
They describe his famous policy of Dhamma. These inscriptions were
installed in prominent places either near towns or on important trade and
travel routes or in the proximity of religious centres and places of
religious importance.