Practitioners of neidan describe a fairly consistent sequence: a gathering warmth in the lower dantian below the navel, then sensations of movement along the spine and over the crown in what is called the microcosmic orbit, and these are reported as involuntary and unmistakable rather than imagined. The literature spends at least as much space on what goes wrong as on the goal. The classic failure is zouhuo rumo — the fire runs wild and demons enter — described with specificity: headaches, heat rising to the head, insomnia, palpitations, uncontrolled shaking, hallucination, and in serious cases psychiatric breakdown. Chinese psychiatry recognised a related category, qigong-induced deviation, and it appeared in the Chinese diagnostic classification. This is the reason the tradition insists on a teacher and warns constantly against forcing, and it is one of the more empirically checkable claims Taoism makes: the practice does something, and doing it wrong has consequences.