1. From Plain Questions (素问 sù wèn, sān bù jiǔ hòu lùn). An ancient pulse-taking scheme. The three positions are three areas on the head, upper limbs, and lower limbs, each area having three pulse points (indicators), which in most cases can be located by the acupuncture point located at the site. See the list below. Possibly owing to a change in mores, the less invasive practice of feeling only the wrist pulse replaced the system of taking the pulse at multiple points, which was probably no longer practiced by the Later Hàn (1st century CE).
2. From The Classic of Difficult Issues (难经 nàn jīng, 18). An ancient pulse-taking scheme. In the context of the wrist pulse, the inch, bar, cubit positions are the three positions, and the superficial level, mid-level, and deep level of each of these are the nine indicators.