Meridian Sash

Dark blue silk, long, with one hairline of white thread running its whole length, and the thread hangs north and south wherever it is tied.

The wearer holds and recalls any chart, table, or reckoning exactly as read. The sash keeps its own running reckoning of every mile it is carried, and answers one question of position, distance, or timing without error - where a thing is now, how far off, and how long until it arrives - though it will not answer twice about the same thing until the wearer has slept.