Figure 18. Chart of pulse variations, 2nd century C.E. Chart categorizing the 15 pulse variations within the Five Phases: 1. Floating (metal); 2. Like a bow-string (wood); 3. Weak (water); 4. Slow (earth); 5. Hollow (fire); 6. firm (wood) 7. Deep (water); 8. Hidden (wood); 9. Smooth (water); 10. Extensive (fire); 11. Gentle (earth); 12. Damp (water); 13. filled in (fire); 14. Rough (metal); 15. weak (metal). Adapted from the Tuzhu nanjing maijue (Classic of Difficult Issues and Pulse Doctrine).