So learn DR Navigation. And practice it always when underway. It will help you find the port you are shooting for without all of those modern gadgets.
You only need to know: Time, Speed and Course to find your way.
Yes but the guy we're discussing never had any instruments. How do you get time, speed and course without instruments? DR without instruments is like a party without people. It ain't gonna happen.
Statistically, the current that runs along the equator moves more water than the collective volume of every river in the world. How do you DR that without instruments?
I said it in one of my earlier posts and I agree with SimonV, this voyage had a great deal of luck involved. And Simon, your checking "once or twice a day" amounts to over 500 possible checks that the instrument-less circumnavigator couldn't do. Remember he was at sea for one and a half years. Go figure.
Thor Heyerdahl did a significant voyage on a papyrus (or something) raft and was also declared a super-navigator. But if he hadn't of drifted into the island his voyage ended on, he would have drifted into another with the same claim to fame - eventually he had to hit something. He may have been dead by then but he would have made landfall somewhere
DR is a science that requires numbers - no numbers, no DR. Simple.