On Mar 12, 2021, Master Chen was instructing on an exercise, in which, I put up my left forearm in front of and parallel to my chest. I need to push the elbow downwards with a pivot in the middle of my forearm, with the load on the hand. The desired outcome requires me to create an independent setup of a lever, and then press down on one side of the lever (elbow). This is separation of yin and yang because the downward force is independent of the lever setup. The lever setup cannot break or change its integrity when the downward force is applied. The outcome of the lever action is predetermined by the setup. The downward force when applied in a specific way simply makes it happen. If the downward force is not applied correctly or the lever setup breaks down, the desired outcome will not happen.
If the forearm itself is considered as 1 (wuji), the downward force being the trigger creates the lever, which is 3 (taiji). There is actually no lever until there is a pivot, one side goes up, and the other side goes down.
The difficulty in this exercise is that there is only one forearm (by locking the wrist and stretching the finger, they become part of the forearm), the pivot is not realized until there is movement on the forearm, and the pivot only exists within the forearm.
How to do it then?
Aim/push the downward energy into the dot, only then the pivot can be realized, and only then the energy can actually pass through to the other side.
Being able to do this allows me to relate other drills together, such as pushing the shoulder into the elbow that is sitting on the table, the hands being on the track when the torso goes down during double downward squeeze. There was also another demonstration that Master Chen has done before using a staff with the opponent standing on the other side holding the staff. He could twist the staff in a way that controls the location of the non-moving dot where the power meets.