Here is a symbol of tremendous antiquity which is worthy of
notice. It is borne on the Korean ensign and merchant flag, and
has been adopted as a trade sign by the Northern Pacific
Railroad Company, though probably few are aware that it is the
Great Monad, as shown in the sketch below. This sign is to the
Chinaman what the cross is to the Christian. It is the sign of
Deity and eternity, while the two parts into which the circle is
divided are called the Yin and the Yan—the male and female
forces of nature. A writer on the subject more than three
thousand years ago is reported to have said in reference to it:
"The illimitable produces the great extreme. The great extreme
produces the two principles. The two principles produce the four
quarters, and from the four quarters we develop the quadrature
of the eight diagrams of Feuh-hi." I hope readers will not ask
me to explain this, for I have not the slightest idea what it
means. Yet I am persuaded that for ages the symbol has had
occult and probably mathematical