Defeat 1000lbs with a trigger force of 4oz vs turning on 4oz we can weigh 1000 lbs.
It's that second part that I'm chewing on today.
When Cheng Man Ching was asked about 4oz defeating 1000lbs he said it was like a rope through a ring in the nose of a bull. The soft pull at a sensitive place motivates the living creature to move where we want it and it can't use its immense strength.
In practice, many players strive to put only 4oz of pressure on their opponent at any time, or allow no more than 4 oz to land on them.
I was going through "Yang Family Secret Transmissions" and musing on the songs. (Side Note: I must be feeling emotional because the Song of Split brought actual tears to my eyes...)
The Song of Pull-Down
How can we explain the energy of Pu ll-down ?
Like weighing something on a balance scale,
We give free play to the opponent's force
whether great or small .
After weighing it we know its lightness
or heaviness .
Turning on only four ounces,
We can weigh a thousand pounds .
If we ask what is the principle behind this,
We discover it is the function of the lever.
I don't speak or read chinese and while I have access to the original text I don't know where it is in the collection of completely unindexed pages of chinese text.
The key point I'm focusing on is the possible different meanings of weigh.
Earlier in the song it refers to weighing something to find it's weight/force/energy. In the second context "We can weigh a thousand pounds" can mean we find the weight OR we can apply a force equal to that weight.
The accompanying picture shows the hapless student fully extended with Yang Cheng Fu holding his wrist down.
This should be self evident, even a small load applied at the extreme end of a lever will exert a force that increases the closer one gets to either side of the fulcrum. The opponent's arm is the lever, their waist is the fulcrum. Yang Cheng Fu is applying the load the far end of the lever, the waist cannot hold against that force. In context Yang Cheng Fu would create this defect position by leading and pulling.
The other side of that is lifting, such as in a posture like "play guitar" in some applications.
The main idea is that our opponent is extending into our space giving us a huge lever to use to manipulate their body.
In this case how I see it is in response to a pull on our right arm, we yield to it briefly, then with the right wrist pull their arm into our sphere of control, put our left hand on the elbow, then pull down on the wrist and push up on the elbow as we sit our weight into the back leg. With a good connection it will feel like throwing a shovel full of dirt.
This works due to levers on levers on levers in the movement and application, the sinking into the back leg powers both the pulling down of the right arm and the lifting of the left arm, so you're starting this force equation with a mass equal to your weight moving, multiplying that force through the mechanical advantage of the lever action of your arms inside your body (stand like a scale, move like a wheel... two applications of the lever), and then multiplying the effect of those forces through the mechanical advantage gained by expressing that force in opposing vectors and applying it to your opponent's ready-to-be-beaten posture, i.e. their weak extension into your sphere of power and control.
I tried to diagram that but I got lost in the arrows and labels, you'll have to just envision it yourself looking at Yang Cheng Fu's glorious Dad bod.
Oh, and the teary part of split was this
Whirlpools appear in swift flowing streams ,
And the curling waves are like spirals .
If a falling leaf lands on their surface ,
In no time it will sink from sight .