I'm thinking specifically of the Azores and Madeira Isles, because they strike close to home (am Portuguese), and how they were discovered (or re-discovered) by men in small ships. Looking at their size in the middle of the Atlantic Ocean makes me wonder what were the processes used by the captain to decide where to go, out of the blue sea. It boggles my mind even further to think of the tiny isles in the much larger Pacific Ocean.

I can think of birds and cloud formation above the isles, as well as possible breeze due to the presence of land, but I wonder if there were other methods used.