{
  "name": "Eratosthenes' 252,000 stadia under four stadion lengths",
  "desc": "Four stadion lengths reported or implied in the 1855 translators' notes to Pliny, each with its source and how much of it was read, the length in meters, the circumference that 252,000 stadia gives and the difference from the WGS 84 meridian circumference. The stadion length is contested; these are scenarios, not findings.",
  "lic": "CC BY 4.0",
  "lic_url": "https://creativecommons.org/licenses/by/4.0/",
  "by": "The Yardstick Almanac",
  "url": "https://theyardstickalmanac.com/scale/eratosthenes-earth-circumference/",
  "from": [
    "Pliny, Natural History, Book 2 (chapters 21, 75, 112, 113) and translators' note 261, trans. Bostock and Riley 1855 (Project Gutenberg #57493), public domain",
    "Yard 0.9144 m and inch 25.4 mm, exact equivalents effective July 1, 1959 (24 FR 5348)",
    "WGS 84 ellipsoid a = 6,378,137 m, 1/f = 298.257223563, from PROJ 9.8.1 src/ellps.cpp (MIT; values correspond to NGA TR8350.2)"
  ],
  "how": "Compiled by The Yardstick Almanac from the data listed",
  "data_by": [
    "Pliny, Natural History, trans. Bostock and Riley 1855 (public domain); WGS 84 parameters from PROJ 9.8.1 (MIT); computed 2026-11-01, CC BY 4.0"
  ]
}