The Classics say:

Heaven is superior. Earth is inferior.

Yang is odd and Yin is even

One and Six share a common ancestor

Two and Seven are comrade

Three and Eight are companions

Four and Nine are friends

Five and Ten are on the same route/path

Closed and open, odd and even

Produce and grow the 5 omens

Prevalent from the beginning to the end

The eight substances widely disseminate

Child and mother branch to bestow

Heaven and Earth orientate and has a relative fixed position

Mountain and Marsh keep each other inform sympathize with each other

Thunder and Wind going hand in hand

Water and Fire do not shoot each other

Middle five establishes the (centre) pole

It arrived and establishes the four directions

One is at the back and nine is at the face

Three and seven reside at the side

Two, eight, four, and six

Vertically and horizontally rules and regulates or arrange the drawstring of the net.

Yang ministers to yin.

Yin nurses yang.

Yang is born in Yin

Soft is born from strong

Yin virtues widely give relief.

Yang virtues are favourable.

Therefore,

Yang's root is Yin

Yin gives birth to Yang

Heaven depends on form

Earth relies on qi.

This is called 'transforming the beginning.'