The original article in the encyclopedia is short, and mine will not be longer. As always, I am interested in the time of event, the reliable source, pronunciation, and all actual information I can place somewhere in my head close to what I have been already learnt.
This time a sinologist Catherine Despeux helps again:” Liànqì 鍊氣 designates a technique for purifying the breath (or pneuma) throughout the body. In the Tan period (618-907), the Yanling xiansheng ji xinjiu fuqi jing (Scripture on New and Old Methods for the Ingestion of Breath Collected by the Elder of Yanling) describes the method as follows: “Harmonize the breath and swallow it. When you do this, you must practice breath retention (bìqì) for as long as possible. ‘Obscure your mind’ (míngxīn 冥心), stop your thoughts, follow the movement of the breath, release and regulate it…. It is not necessary to practice daily, but mainly when the mind is clear and relaxed, for example every five or ten days.””
This is about paying attention to your breath again, and it is ok if you are an introvert or a divergent at least, otherwise look for something else:))