What did The Incas used to help them remember the important messages that had to go across the Empire?

The Incas used a system of knotted strings called quipus or khipus to help them remember and communicate important messages across their empire. Each knot and string color represented different numerical values or categories of information, allowing for the storage of data related to census, tribute, and resources. This system enabled the Incas to efficiently manage their vast territory without a written language. Quipus were often used by trained officials known as quipu keepers, who could interpret and relay the information encoded in the knots.