Sinking, a concept as important in seated meditation as it is in Taiji, involves, as does every action, a relaxed and a tense component. The relaxed component is simply letting go to gravity with a vertical spine; feeling the draw as a flow of energy. The tense component activates the spinus erectus muscles – the pythons either side of the lumbar spine – to extend the bottom end of the spine down into the earth and the top end upwards out of the crown of the head; rather like driving a stake into the ground. Then, as you work, softly but firmly, the energy of the earth coils itself upwards around your spine like a runner bean creeping up a beanpole or like a dozy snake woken by the charmers shawm. Most practitioners make the mistake of allowing the belly to drift up and back in order to alleviate the strain on the legs, in which case this coiling energy has nothing to coil around. Keeping the bum in – sinking the dantien/sacrum down and forward into the posture and leg(s) – corrects this weakness.