Polynesian stick charts are real things–real amazing things. This is the best post I could find about them online. You can see that I clearly nabbed the design of Tevia’s from the second one down.
“(The) navigator gauged the wave patterns represented in the Stick Charts entirely by his sense of touch. ‘He would crouch in the bow of his canoe and literally feel every motion of the vessel.’ As with ripples in a pond they’concentrated on refraction of swells as they came in contact with undersea slopes of islands and the bending of swells around islands as they interacted with swells coming from opposite directions.’”