The magic square,

4 9 2
3 5 7
8 1 6

played an important part in the development of mathematics in ancient China. Legend has it than an Emperor Yu recieved this magic square from a Lo River Tortoise. It was part of a series of diagrams called the Lo Shu which contained the foundations of Chinese mathematics.

The important thing about this particular magic square is it led to the devolopment of dualistic theory, ie. Yin and Yang, where Yin is represented by the even numbers and Yang by the odd numbers. Notice how the even and odd numbers are distributed within the square, somewhat like a Yin Yang, in the sense of an even distribution.

Thanks to Falsch Freiheit for pointing out to me how the square also resembles a yin yang with one color being represented by numbers less than five, and the other by numbers greater than five. He says: "4, 3 and 1 are the 'body' of one side, with 8 as the dot in the center, 9 7 6 the 'body' of the other side with 2 the dot in the center." I suppose the five is simply the border between the two bodies.