Traverse board

The traverse board is a memory aid formerly used in dead reckoning navigation to easily record the speeds and directions sailed during a watch. Even crew members who could not read nor write could use the traverse board.

As the mathematician William Bourne remarked in 1571, “I have known within these 20 years that them that were ancient masters of shippes hathe derided and mocked them that have occupied their cards and plattes and also the observation of the Altitude of the Pole saying; that they care not for their sheepskinne for he could keepe a better account upon a board.”