The Taichi Chuan Classic of Wang Zong Yue

Taichi is born of wuji, and is the mother of yin and yang.
When there is movement, the passive and active aspects become distinct from each other. When there is stillness, they return to being indistinguishable.
Neither going too far nor not far enough, comply and bend then engage and extend.
He is hard while I am soft – this is yielding. My energy is smooth while his energy is coarse – this is sticking.
If he moves fast, I quickly respond, and if his movement is slow, I leisurely follow. Although there is an endless variety of possible scenarios, there is only this single principle [of yielding and sticking] throughout.
Once you have ingrained these techniques, you will gradually come to identify energies, and then from there you will work your way toward something miraculous. But unless you practice a lot over a long time, you will never have a breakthrough.
Forcelessly press up your headtop. Energy sinks to your elixir field. Neither lean nor slant. Suddenly hide and suddenly appear.
When there is pressure on the left, the right empties. When there is pressure on the right, the left disappears. 
When looking up, it is still higher. When looking down, it is still lower. When advancing, it is even farther. When retreating, it is even nearer.
A feather cannot be added and a fly cannot land. The opponent does not understand me, only I understand him. A hero is one who encounters no opposition, and it is through this kind of method that such a condition is achieved.
There are many other schools of boxing arts besides this one. Although the postures are different between them, they generally do not go beyond the strong bullying the weak and the slow yielding to the fast. The strong beating the weak and the slow submitting to the fast are both a matter of inherent natural ability and bear no relation to skill that is learned.
Examine the phrase “four ounces moves a thousand pounds”, which is clearly not a victory obtained through strength. Or consider the sight of an old man repelling a group, which could not come from an aggressive speed.
Stand like a scale. Move like a wheel.
If you drop one side, you can move. If you have equal pressure on both sides, you will be stuck.
We often see one who has practiced hard for many years yet is unable to perform any neutralizations and is generally under the opponent’s control, and the issue here is that this error of double pressure has not yet been understood.
If you want to avoid this error, you must understand passive and active. In sticking there is yielding and in yielding there is sticking. The active does not depart from the passive and the passive does not depart from the active, for the passive and active exchange roles. Once you have this understanding, you will be identifying energies.
Once you are identifying energies, then the more you practice, the more efficient your skill will be, and by absorbing through experience and by constantly contemplating, gradually you will reach the point that you can do whatever you want.
The basic of basics is to forget about your plans and simply respond to the opponent. We often make the mistake of ignoring what is right in front of us in favor of something that has nothing to do with our immediate circumstances.
For such situations it is said: “Miss by an inch, lose by a mile.” You must understand all this clearly.
This essay contains one crucial sentence after another and does have a single word that does not enrich and sharpen its ideas. But if you are not smart, you will not be able to understand it. The founder did not lightly teach the art, not just because he was discriminating over accepting students, but also because he did want to go to the effort only to have it wasted.