Biruni's measurement of the Earth
Biruni's measurement of the Earth's radius is illustrated here.
At the beginning of the 11th century, Biruni measured the Earth with a precision not surpassed in the west until the 16th century. This illustration shows how the 34′ dip of the horizon that he says he observed from the top of a hill near Nandana Fort is extremely close to that which can be seen from a nearby hill, thus identifying its location. It also illustrates why he got the height of this hill as 652 cubits and 3′18″ (or 321½ m).