What's IIRC?
Apparently there's an entire topic on Erastosthenes:
Curvature Measured in 200BC.
https://www.theflatearthsociety.org/forum/index.php?topic=76513.0
"If I recall correctly." I studied astrophysics in college, I'm not really able to entertain the idea of a flat planet, it just isn't possible. There's lots of math/evidence against it