Biruni's measurement of the Earth
Biruni's measurement of the Earth's radius is illustrated here.
At the start of the 11th century, Biruni measured the Earth with a precision that wasn’t matched in the West until the 16th century. This illustration shows how the 34′ dip of the horizon that he claimed to have observed from the top of a hill near Nandana Fort is remarkably close to what can be seen from a nearby hill, helping to pinpoint its location. It also explains why he determined the height of this hill to be 652 cubits and 3′18″ (or 321½ m).