jm ØuøÀõÅÑaºU/Ë|¢©Åë@`£öEÞ(À;ÊL 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
https://whatsonchain.com/tx/dd6f5a0f3ed0fee61dcd4e6ab55c0a234c9468772b6c18e606fad8ab53b3eb86