|All transit expeditions needed instruments to establish the observers position and to monitor the performance of the clocks. The official instructions of Nevil Maskelyne specifically recommended this type of quadrant made by the leading London maker John Bird.
Captain Cooks mission came close to failure when the quadrant disappeared during its first night on shore in Tahiti. It must have been crystal clear to the Tahitian responsible that this was an exceptionally precious object. After a desperate search the quadrant was dramatically recovered, needing only minor repairs.