The Song of True Meaning of Tàijíquán (太極拳真義訣) by Lǐ​ Dàozi​ (李道子)

One of the difficulties one may encounter when looking at the texts presented as important for the practice is their cryptic language. It can be understood that some of the inner experiences can only be passed on in poetic form. It is also understood that early texts come from oral traditions tend to come in "songs" or texts that are easier to memorize.
For example, this text has the suggestive name of "The Song of True Meaning of Tai Chi Chuan". It certainly attracts attention also because it is reported by two important authors like Yang Jwing Ming (楊俊敏) and Jou Tsung Hwa (周宗樺). So, definetely something that the serious practicant should pay attention to.
In the other hand, beyond the evocations it brings, it is difficult to have an indication of how it should influence our practices. At least, if it is not commented by the practice with a recognized Master.

太極拳真義訣

無形無象，全身透空。
忘物自然，西山懸磬。
虎吼猿鳴，泉清水靜。
翻江鬧海，盡性立命。

李道子

"No shape, no shadow.
The entire body is transparent as air.
Forget your surroundings and be natural.
Like a stone chime suspended from the West Mountain.
Tigers roaring, monkeys screeching.
Clear fountain, peaceful water.
Turbulent river, stormy ocean.
Develop your whole body and mind to their full extent."

From the book The Tao of Tai Chi Chuan" (太極拳之道), by Jou Tsung Hwa (周宗樺) and "Yang Style Tai Chi Chuan" by Yang Jwing Ming (楊俊敏) based on the translations proposed in both books.

The Tao of Tai Chi Chuan and The Tao of Meditation by Jou Tsung Hwa (周宗樺)

Arguably the best book around on the topic of Tàijíquán (太極拳), "The Dao of Tai Chi Chuan" (太極拳之道) is both concise and deep. Its companion "The Tao of Meditation" (靜坐開悟之道) share the same characteristics. The approach is through principles, rather than routines, and the explanations given open the doors for further research. Some of the texts and terms mentioned by Master Jou Tsung Hwa (周宗樺) in the book make reference to ancient and classic works that few other authors dare to approach.
There exists a third volume, called "The Tao of I Ching", which for me seems less interesting, as much in it is quite redundant with other books on the same topic.
Master Jou Tsung Hwa (周宗樺) is one of the exponents of the first generations that brought Tàijíquán (太極拳) to the west, and a major Internal Martial Arts community and festival was initiated by him in the U.S.