When Mr. Qian (Wei-yan) was Governor of the two Zhejiang provinces, he authorized the building of a wooden pagoda at the Fan-tian Si (Brahma-Heaven Temple) in Hangzhou with a design of twice three stories. While it was under construction General Chhien went up to the top and was worried because it swayed a little. But the Master-Builder explained that as the tiles had not yet been put on, the upper part was still rather light, hence the effect. So then they put on all the tiles, but the sway continued as before. Being at a loss what to do, he privately sent his wife to see the wife of Yu Hao with a present of golden hair pins, and enquire about the cause of the motion. (Yu) Hao laughed and said: 'That's easy, just fit in struts (pan) to settle the work, fixed with (iron) nails, and it will not move any more.' The Master-Builder followed his advice, and the tower stood quite firm. This is because the nailed struts filled in and bound together (all the members) up and down so that the six planes (above and below, front and back, left and right) were mutually linked like the cage of the thorax. Although people might walk on the struts, the six planes grasped and supported each other, so naturally there could be no more motion. Everybody acknowledged the expertise thus shown.