《黄帝内经·素问·上古天真论》
中古的时候，有称为至人的人，具有醇厚的道德，能全面地掌握养生之道，和调于阴阳四时的变化，离开世俗社会生活的干扰，积蓄精气，集中精神，使其远驰于广阔的天地自然之中，让视觉和听觉的注意力守持于八方之外，这是他延长寿命和强健身体的方法，这种人也可以归属真人的行列。
中古之时，有至人者，淳德全道，和于阴阳，调于四时，去世离俗，积精全神，游行天地之间，视听八达之外，此盖益其寿命而强者也，亦归于真人。
In the Middle Ages, there were people called "Zhiren" who had a pure morality, who could fully master the way of health preservation, and who could reconcile with the changes of the four seasons of yin and yang, leave the interference of secular social life, accumulate essence and energy, concentrate their spirits, and make them travel far away in the vastness of nature. The attention of vision and hearing is maintained outside the eight directions, this is his method of prolonging life and strengthening the body, and this kind of person can also be attributed to the ranks of true people.