A more thorough explanation:

The Black Book of the Exchequer is a historical record book that contains important English state documents such as treaties, conventions, charters, and papal bulls. It dates back to the 13th century and is also known as Liber Niger Parvus.

Examples of documents that can be found in the Black Book of the Exchequer include:

• A treaty between England and France
• A charter granting land to a nobleman
• A papal bull granting special privileges to a religious order

These examples illustrate how the Black Book of the Exchequer was used to record important state documents that were crucial to the governance of England. It was a way to keep track of agreements, grants, and other important information that could be referred to in the future.