Khipu (Quipu) Field Guide

this is about a "writing system" used by the inca that was based on making knots on string and knotting strings together to form a tree. It is read by touching the knots with your fingers, not unlike braille. Most of the written corpus seems to be census records and commercial transactions.

By far, it's the most surprising and exotic writing system i ever heard of.

https://en.wikipedia.org/wiki/Quipu