Important to know if you’re into studying Chinese Religion, or if you want to understand some of the stuff going on in Chinese Xianxia webnovels.
The author’s great teacher, Daoist master Sung Jin Park, described the Three Treasures by comparing them to a burning candle. Jing is like the wax and wick, which are the substantial parts of the candle. They are made of material, which is essentially condensed energy. The flame of the lit candle is likened to qi, for this is the energetic activity of the candle, which eventually results in the burning out of the candle. The radiance given off by the flaming candle is shen.
Most longevity practices therefore work on the basic stuff of qi in some fashion, by processes typically involving its ingestion, circulation, and refinement in the biospiritual organism. If the adept can purify qi in himself, or if he can ingest and store the refined qi of herbal or mineral substances (whether in their natural states or as improved by esoteric methods)—fortified, either way, with the essences ( jing) that result from such refinements—he can become a longevous being qualified to ascend into the higher reaches of the heavens, where the qi is subtler and purer.
Campany, R. F., & Ge, H. (2002). To live as long as heaven and earth: A translation and study of Ge Hong’s traditions of divine transcendents. Berkeley: University of California Press.