身靈
身滯則進退不能自如，故要身靈。舉手不可有呆像,彼之力方礙我皮毛，我之意已入彼骨裡，兩手支撐，一氣貫穿。左重則左虛，而右已去；右重則右虛，而左已去。氣如車輪，周身俱要相隨，有不相隨處，身便散亂，便不得力，其病於腰腿求之。先以心使身，從人不從已。後身能從心，由已仍是從人。由己則滯，從人則活。能從人，手上便有分寸；稱彼勁之大小，分釐不錯，權披來之長短，毫發無差；前進後退，處處恰合，工彌久，而技彌精矣。
李亦畬
"Second saying: agility of the body
If the body is stagnant, then one cannot move forward and backward smoothly, this is the reason why it is important for the body to be agile. Raising one’s hand should not look dull. As the opponent’s power just block my skin, my intention has already entered deep in his bones. Both hands support a single thread of unified Qi from beginning to end. If the opponent weights on the left, one voids the left and let the right go; it the opponent weights on the right, one voids the right and let the right go. Qi is like a wheel, each part of the body must follow one another. If one part does not follow, then the body is disorganized, it is not possible to gather force. If one has this problem, then the waist and legs must be investigated. First one uses intention to send instructions to the body to follow the opponent and not follow ones’s will. Afterwards, the body may follow the will, because it still follows the opponent. If one follows oneself, then the movement is sluggish, if one follows the opponent then the movement is lively. If one is able to follow the opponent, then top of the hand is very precise. When one weighs the opponent strength (Jin), one should distinguish the hundredths of it correctly and sense the power’s duration, when sending out there will not be an error even by a hairsbreadth. Going forward and backward, in all respects perfectly coordinated. The longer one works, the finer the skill."
By Lǐ Yìyú (李亦畬), based on the translation by by Yang Jwing Ming (楊俊敏) presented in the book Tai Chi Secrets of the Wu/Li Style (太極拳武李氏先哲秘要) and various translations on the internet