The first major inscription in classical Sanskrit is that of Rudradaman. Rudradaman was a ruler of the Western Kshatrapas, a dynasty that ruled parts of modern-day Gujarat and Rajasthan in India during the 2nd century CE. His inscription is known as the Junagadh Rock Inscription.

Background:
During this period, Sanskrit was primarily used by the Brahmins and scholars for religious and literary purposes. The rulers and administration mostly used Prakrit, a vernacular language, for official purposes. However, Rudradaman's inscription marks a significant shift as it is written entirely in classical Sanskrit.

Content of the Inscription:
The Junagadh Rock Inscription is carved on a large boulder located in Junagadh, Gujarat. It consists of 14 lines written in Brahmi script, a writing system used for various Indian languages during that time.

The inscription starts with an invocation to Lord Vishnu and provides details about Rudradaman's lineage and his conquests. It mentions his victory over the Shaka rulers and the restoration of his kingdom. The inscription also describes his military achievements and his patronage of religion and Brahmin scholars.

Importance of the Inscription:
The Junagadh Rock Inscription is historically significant for several reasons:

1. Classical Sanskrit: This inscription is the earliest known example of a major inscription written in classical Sanskrit. It demonstrates the growing influence of Sanskrit as a language of power and administration during that period.

2. Political History: The inscription provides valuable information about the political and military history of Rudradaman and his kingdom. It highlights his successful campaigns against the Shakas and his efforts to consolidate his power.

3. Cultural Patronage: Rudradaman's inscription reveals his patronage of religion and Brahmin scholars. It showcases the close association between political power and religious authority during that era.

4. Linguistic Evolution: The inscription provides insights into the linguistic evolution of Sanskrit from Vedic Sanskrit to classical Sanskrit. It shows the development of Sanskrit as a refined and standardized language for literary and administrative purposes.

In conclusion, the first major inscription in classical Sanskrit is that of Rudradaman, known as the Junagadh Rock Inscription. This inscription is historically significant as it marks the use of classical Sanskrit in official and administrative contexts, providing valuable insights into the political and cultural history of the time.