Taiji Lun by Wang Tsung-yueh
Taiji (The Great Ultimate) comes from Wu Chi (Undifferentiated Oneness)
and is the mother of yin and yang.
In motion Taiji separates;
in stillness yin and yang unite and return to Wu Chi.
It is not excessive or deficient;
it follows a bending and adheres to an extension.
When the opponent is hard and I am soft,
it is called yielding.
When I follow the opponent and he becomes backed up,
it is called sticking.
If the opponent's movement is quick,
then quickly respond;
if his movement is slow,
then follow slowly.
Although there are innumerable variations,
the principles that pervade them remain the same.
From familiarity with the correct touch,
one gradually comprehends jing (energy);
from the comprehension of jing one can attain wisdom.
Without long practice
one cannot suddenly understand Taijiquan.
Without effort the jing reaches the top of the head.
Let the qi (vital life energy) sink to the dantien (field of elixir, just below the navel).
Do not lean in any direction;
Empty the left wherever a pressure appears,
and similarly the right.
If the opponent raises up, I seem taller; (Looking up it is higher and higher)
if he sinks down, then I seem lower; (Looking down it is deeper and deeper)
advancing, he finds the distance seems incredibly long;
retreating, the distance seems exasperatingly short.
A feather cannot be placed,
and a fly cannot alight
on any part of the body (without setting it in motion).
The opponent does not know me;
I alone know him.
To become an invincible boxer results from this.
There are many boxing arts.
Although they use different methods,
for the most part they do not go beyond
the strong dominating the weak,
and the slow resigning to the swift.
The strong defeating the weak
and the slow hands ceding to the swift hands
are all the results of natural abilities
and not of well-trained techniques.
From the sentence "A force of four ounces deflects a thousand pounds"
we know that the technique is not accomplished with strength.
The spectacle of an old person defeating a group of young people,
how can this be attributed to speed?
Stand like a balance and turn like a wheel.
Sinking to one side allows movement to flow;
being double-weighted is sluggish.
Anyone who has spent years of practice and still cannot neutralize,
and is always controlled by his opponent,
has not corrected the fault of double-weightedness.
To avoid this fault one must distinguish yin from yang.
To stick means to yield.
To yield means to stick.
Within yin there is yang.
Within yang there is yin.
Yin and yang mutually aid and change each other.
Understanding this you can say you understand jing.
After you understand jing,
the more you practice,
the more skill you will attain.
Silently treasure knowledge and turn it over in the mind.
Gradually you can do as you like.
Fundamentally, one must give up oneself to follow others.
Most people mistakenly give up the near to seek the far.
It is said, "Missing it by a little will lead one many miles astray."
The Taijiquan practitioner must study carefully.
This is the Treatise.