73) “In 1872 Capt. Gibson and crewmates, sailing the ship “Thomas Wood” from China to London, reported seeing the entirety of St. Helena Island on a clear day from 75 miles away. Factoring in their height during measurement on a ball-Earth 25,000 miles in circumference, it was found the island should have been 3,650 feet below their line of sight.“
If the numbers are actually correct (impossible to factcheck), a distance of 75 miles (120km) accounts for a curvature drop of 1.13km. Factoring in minimal refraction (sources and calculations see Point 69 and Point 70) gives an extra 150m.
St. Helena is 823m above sealevel (+ 150m refraction), for the ship let's take a crow's nest of 10m height. Add it up and you get 111.4+11.3 = 122.7km. That means it's visible even under minimal refraction influence.