keyshape

Navigational Chart (Rebbilib), Republic of the Marshall Islands 19th–early 20th century, Coconut midrib, fiber (more info via Metropolitan Collection Database)

"This example consists of a gridlike structure of seven vertical sticks lashed to four horizontal ones. The corners extend outside the main grid, while three curved strips, possibly representing the patterns of ocean swells, extend from side to side. The intersections created by the slanting sticks at the corners may indicate the locations of specific islands. In some instances, small cowrie shells, absent on this example, are also used to indicate the positions of individual islands.

ProvenanceKay Sage Tanguy Estate, 1963; The Museum of Primitive Art, New York, 1978."

thanks to I'M REVOLTING archives for reminding me that i visited the met on at least 3 occasions last year to see this.