In the coastal mountains overlooking the Black Sea there lived a beautiful Circassian woman whose husband had, by the art of magic, been turned into a donkey. From her house she could just make out the port city of Trebizond, 40 miles away on the horizon, for they lived 0.2 miles above the water.
One day a Mullah, who was passing by, saw the Circassian woman weaving baskets (for this was how she made her living) and fell in love with her. Wishing to engage her in conversation, he inquired as to the diameter of the earth.
Sir, said the woman (who immediately suspected what the Mullah was up to) according to ancient Circassian wisdom, the diameter of the earth is equal to the square of the distance to the horizon divided by the height of the eye. But squaring the 40 miles to the City, so precisely on the horizon, gives 1600, which divided by the height of this headland, is 8000 miles. Therefore, reverend Sir, earth's diameter must be 8000 miles, praise Allah the just and merciful!
However, she continued, you had better not try flirting with me because the donkey here is my husband and he will kick you flying a hundred miles a minute over the Rhododendron Forest and the Pontic Mountains.
And in fact the caravan route from Trebizond through the Pontic mountains to Tabriz in Persia does pass through a forest of rhododendron.
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note: the woman and her husband did indeed live 40 miles from Trebizond as the crow flies, but to be more precise their elevation was 0.203 miles, and the earth's diameter closer to 7880 miles. The woman knew this but judged that the Mullah neither needed nor deserved to be told with such precision. There is a nice explanation of the ancient Circassian wisdom at a NASA site:
http://www-istp.gsfc.nasa.gov/stargaze/Shorizon.htm
This will make it clear to anyone unfamiliar with the fact that the diameter of the earth is the square of the distance to the horizon divided by the height of the eye.