The master Sea-Ling, when teaching his scholars the secrets of Ying and Yang, would use two brass tubes and a steel ball to demonstrate the principles of opposing forces working in unison.
Two decorative brass tubes were handed t the students one representing the force of Ying and the other the force of Yang. A loose fitting steel ball falls freely through each tube. However when the tubes are placed end to end on top of each other, the forces align and disturbances in time, space and matter occur.
To demonstrate this the student holds the tubes in alignment and Sea-Ling drops the ball into the top opening. Instead of falling through the bal remains in the tubes until released by a snap of the masters fingers. The master then holds the tubes and the student places the ball into the top tube. This time the ball falls slowly that Sea-Ling is able to raise one tube above the other and keep the ball traveling through the tubes.
As a final demonstration, the student is invited to drop the ball himself and watch the ball float slowly down the tubes. When the tubes are separated, everything returns to normal.