I've reviewed tons of lake laser tests, boat sighting tests, bridges going away from the camera, etc. The issue with all of these is you can cherrypick them to make your point either way: globe or flat. They're too dependent on variables like index of refraction and mirage effect. Therefore, I've chosen to completely ignore all of them. But I'll put some here just because.
Need to test a fair amount above the lake to remove refraction from water vapor Proof: https://youtu.be/KLufSkz-et0 https://www.metabunk.org/refraction/
Also 8 inches per mile squared doesn't consider observer height. The ground will actually rise up first because you're moving the tangent line upward and tilting downward. This is why using a calculator or equations that factor height in is required.
https://the-uncredibles.tumblr.com/post/130511368809/200-pensb-13-biot-and-arago-experiment
8 inches per mile squared doesn't account for observer or target height. This alleged experiment doesn't seem to have proper documentation beyond a short summary, but it's relatively easy to see certain things 100 miles away when elevated over 2000 feet, which is one of the elevations involved.
The other unspecified elevation would have to be about 1600 feet for it to work.
The length of some of the sides of the great triangles (in the English survey) is upwards of 100 miles; and many means were employed to render the stations visible from each other at such great distances. The oxy-hydrogen, or Drummond’s Light, was employed in some instances; but a heliostat, for reflecting the sun’s rays in the direction of the distant observer, was more generally and successfully employed. Lieutenant-Colonel Portlock, R.E., who observed the station on Precelly, a mountain in South Wales, from the station on Kippure, a mountain about 10 miles south-west of Dublin–the distance between the stations being 108 miles–says: ‘For five weeks I watched in vain; when, to my joy, the heliostat blazed out in the early beams of the rising sun, and continued visible as a bright star the whole day.’
Kippure is a single mountain (2,484 feet),
Preseli range: highest peak in the range has a height of 1,759 feet and there are two other peaks with heights above 1,500 feet.
Minimum target height would be 1437 feet.