The question asks to identify the earliest text that proposed paying cash salaries to government officers.
The Arthasastra, an ancient Indian treatise on statecraft, economic policy, and military strategy, attributed to Kautilya (or Chanakya), is renowned for its comprehensive coverage of administrative practices.
This text provides detailed accounts of:
While other texts like Manu Smriti, Kamandaka Nitisara, and Nitivakyamrita also discuss aspects of governance and law, the Arthasastra is considered the seminal work that first systematically detailed the practice of fixed cash payments as salaries for state officers.
Therefore, the Arthasastra is the correct answer.