Among all the sources used by historians, which are considered the most valuable for understanding the Mauryan Empire?
1) Ancient coins and artifacts
2) Contemporary accounts of foreign travelers
3) Sculptures and paintings
4) Asoka's inscriptions on rocks and pillars

Choose the correct answer from the given options:

4

Historians have employed diverse sources to piece together the history of the Mauryan Empire. These sources encompass archaeological discoveries, notably sculptures, and contemporary accounts like the fragmented records of Megasthenes, a Greek ambassador to the court of Chandragupta Maurya. Additionally, the Arthashastra, possibly composed by Kautilya or Chanakya, traditionally believed to be Chandragupta's minister, is a valuable resource. References to the Mauryas can also be found in later Buddhist, Jaina, and Puranic literature, as well as in Sanskrit literary works. However, the inscriptions of Asoka, dating from around 272/268-231 BCE and etched on rocks and pillars, are regarded as among the most precious sources.