Kai Ying Tung 董繼英 . The only available video clip of pushhands.

Kai Ying Tung 董繼英 Dong Jiying. Hong Kong/Los Angeles. Grandson of Tung Ying Chieh 董英傑 who was senior student of Yang Chengfu.

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'
http://thetaichiworkshop.dk/

"Move the qi like a nine swirled p...