The Inkas may have used clusters of strings and knots (called khipu) as their way of recording language, while most other cultures of the world have used written records of ink on paper. This suggestion is described in 1491: New Revelations of the Americas Before Columbus by Charles C. Mann, Appendix B.
Honestly, I have never stopped to think about representing language in terms of objects versus written symbols, but the concept of creating a physical system for recording thoughts is actually quite inspiring. It reminds me of the way genes are encoded in long strands of DNA, although this system sounds like it has many more base elements to it. These elements include the kind of material used, the way the strings were spun, and the direction of the knots attached to all the other strings in the khipu. There were also, apparently, 24 different string colors.
It makes me think that it might be interesting to create a kind of khipu myself. The Inka's khipu sound fairly complex however; each khipu which has been found encoded one of 1,536 possible "distinct information units"!