James Cook set sail from Plymouth in August 1768 aboard HM Bark Endeavour with a mission that was officially about astronomy — observing the transit of Venus from Tahiti. The second set of orders, sealed and not to be opened until the astronomy was done, told him to search for the undiscovered southern continent that European geographers were convinced must exist. He didn't find it. He did find New Zealand, the east coast of Australia, and charted more of the Pacific than anyone before him. The transit of Venus data was inconclusive.
