Quipu

The Inca used a system of knots to record numerical data and metadata, called quipu. Here's one I made to record all the elevations of the places I visited in Peru while on vacation there.

They're in chronological order, starting with the first place I visited on the leftmost vertical hanging rope, Lima, with its elevation notated by counting the number of knots, the type of knot, and how they are spaced apart.