Tai Chi push-hands, in Chinese tuishou 推手, consists of circular movements performed by two players. It involves martial arts techniques derived from the various forms, but Tai Chi is an internal martial art, which means that the techniques relies on internal energy, chi or qi 氣, not solely strength of the muscles. The principles for developing and using the chi is described in the Tai Chi Classics.
Some important texts were written by members of the Chen, Yang, and Wu (武) families, but the oldest classics are the ones from the Li family who trained martial art in the Thousand Year Monastery together with their cousin Chen Wangting.
You can read much more about the original classics in ‘Tai Chi – The True History and Principles’
“Move the qi like a nine swirled pearl (spiral)- let there be no part it does not reach.
Move the energy like folding steel a hundred times, such steel is tough and will not break.
Your body has the appearance of an eagle seizing a rabbit.
Your spirit must be like a cat catching a mouse.
Be still like a mountain peak and move like a flowing river.
Store the energy like bending a bow.
Release the energy like releasing an arrow.
Aim straight in the middle of the arch, build up and let go.
The force releases from the back, the steps follow when the body shifts.
Gather then release it, reconnect when connection is broken.
When moving back and forth there must be a continuous connection.
When advancing and retreating there must be constant shifts.
First be extremely soft then extremely hard.”
From the classic ‘Explaining the mind-set of the practice of the
thirteen movements’ by Li Zhong 李仲 (1598-1689) – cousin of Chen Wangting.