Sentence:  Instead of linking the nine numbers of this diagram with the traditional Nine Provinces , as was usually <WSD>done</WSD> , this equated the odd , Yang numbers with mountains ( firm and resistant , hence Yang ) and the even numbers with rivers ( sinuous and yielding , hence Yin ) ; taking the former from the Five Sacred Mountains of the Han period and the latter from the principal river systems of Old China . 
Meaning of the word marked with <WSD> tags:  engage in