The foundational principles of tai chi were written in a collection of writings called the tai chi classics. Some of these pages were found in a corner of a salt store near the Chen village in China in the nineteenth century. The tai chi classics are the historical wisdom of the old masters that in a very cryptic way tell us what we should include within our practice.
Nowhere in the classics, beyond the 13 postures, are the names of the various tai chi techniques, movements and methods mentioned. We are only given generalised taoist chi gung principles, philosophical concepts, and fighting strategies. Even the original 13 postures mentioned in the classics are not presented as specific how-to instructions; rather they refer to general internal energy principles.
Some examples of writings contained within the classics include;
in motion the whole body should be light and agile, with all parts of the body linked as if threaded together.
~ t’ai chi ch’uan ching (attributed to chang san-feng c.1279-1386)
tai chi comes from wu chi and is the mother of yin and yang. In motion tai chi separates; in stillness yin and yang fuse and return to wu chi.
~ treatise on tai chi chuan (attributed to wang tsung-yueh)
when moving, there is no place that does not move. when still, there is no place that is not still. first seek extension, then contraction;
then it can be fine and subtle.
~ insights into the practice of the thirteen postures (wu yu-hsiang)
pay attention to the waist at all times; completely relax the abdomen and the chi rises up. When the tailbone is centered and straight, the spirit goes through to the headtop. To make the whole body light and agile suspend the headtop. Carefully study. Extension and contraction, opening and closing, should all be natural.
~ song of the thirteen postures (unknown)