The Yang Family Manuscripts are known as The Tai Chi Classics they are the historical writings of the old masters. They are the technical manuals which let us know what we should have within our art so that we can practice it correctly.
A much more detailed explanation of The Tai Chi Classics is contained within The Training Manual of The College of Chinese Martial Arts
What the classics say about fighting
Stick, connect and adhere to the opponent, draw the opponent in, attack with great force. Use spiral movements attack the opponents neck. Always maintain close contact but never grapple, use fa jin.
Be like a speeding horse destroying all in its path. Attack the opponents acupuncture points with the hand techniques of break, bend, beat and pound, press down, rub, push and grab, open and close, rise and fall.
Applications for palm are strike down and forwards, applications for fingers are seek and stab the acupuncture points, applications for whole hand are break and drain opponents chi, applications for fist is to punch. Among punches there are, down and parry punch, below elbow punch, turn the body punch, upside down punch, open mountain punch, under leaf punch, reverse punch, power portion punch and rolling break punch. Remember the footwork follows the body.
Every move is an attack, destroy all in your path. Use elbow to take his life. Leave your opponent no room to escape, strike without mercy. The hand like a swift sword, slicing across the forehead or throat, send the opponent straight to hell.
Use an attack no opponent can withstand making sure not to give the opponent an opportunity. Like a tiger pouncing on sheep, like a speeding horse destroying all in its path.
You must understand the life and death hand techniques, you must understand the life and death acupuncture points. Attack the points so life is no more.
What the classics say about Chi Kung
The elixir of life lies in the body, regulate the chi and the body will be well.
Develop the body and mind, cultivate ones essence, chi and spirit. Train the martial and the spiritual, for self cultivation in tai chi balance yin and yang to rejuvenate.
The whole body is filled with chi, the changes of yin and yang move the chi. The chi spirals in the body like the coils of a snake. The hips, waist and belly are like a dragon twisting its body.
Be like a swimming dragon. Inhale the chi to the tan tien, exhale to fa jin.
What the classics say about sensitivity training
Remain internally reserved, contain hardness without expressing it, meet the opponent with softness causing him to know nothing of you.
With the opponent rise and drop, speed up and slow down, evade and return, provoke and cease.
Use adhering, connecting and following to attain this skill. Learn to interpret chi, use the eyes correctly, listen with the skin and remain balanced at all times.
Increase your chi and keep your mind strong, drain the opponents chi and drain his strength. We are victorious, the opponent fails.
What the classics say about moving with the opponent
Strike the opponent when his attack is imminent but has not yet issued forth. The whole body must fa jin when attacked, this is an internal skill. To defeat the opponent one must be able to interpret his chi.
Relate to the opponent with turn and exchange, advance and retreat. Know his hands forwards and backwards intention by gaze left but look right. Attacking the opponents blood vessels and acupuncture points and he will faint, forceful attacks on the death points terminate the opponents life.
What the classics say about ones own body movement
Spine straight and vertical, sink the chi to the tan tien. Raise ones spirit and turn the waist/hips/belly continuously. Be like a swimming dragon twisting its body be flexible and soft, the body follows the chi, the chi follows the spirit.
A much more detailed explanation of the whole system of Tai Chi Chuan is contained within
The Training Manual of The College of Chinese Martial Arts