A more thorough explanation:

An actuarius is a person who works as a notary or clerk. They are responsible for keeping public records. In ancient Rome, actuarii were important officials who recorded legal proceedings and other important events.

• When a person buys a house, an actuarius is often present to record the transaction.
• In ancient Rome, actuarii were responsible for recording the proceedings of the Senate and other important events.

These examples show how an actuarius is responsible for keeping records of important events. They are like a historian who writes down what happened so that people can refer to it later.