 A meditator visualizes or actualizes solar and lunar essences, lights, and deities within their body, which supposedly results in health and longevity, even "xian" 仙/仚/僊, "immortality".The (late 4th century BCE) "Guanzi" essay "Neiye" "Inward training" is the oldest received writing on the subject of "qi" cultivation and breath-control meditation techniques.For instance, "When you enlarge your mind and let go of it, when you relax your vital breath and expand it, when your body is calm and unmoving