Although the descriptions of shigyakukachotanto in “Waitaimiyaofang” and tsumyakushigyakukachotanjuto in “Songban Shanghanlun” are quite similar to each other, the specifications of the dosages of crude drugs and the water volume in the books were considerably different. Focused on the specified water volume to decoct these formulas, each reasonable decocting period was estimated, then the decoctions were prepared using hard water that was common in mainland China. The dosages of aconite root were 2­-fold different between these two formulas, but the contents of aconitine-­type diester alkaloids (ADA) in both decoctions were found in the range of 1.2—1.4­-fold. It was suggested that in order to control the efficacy and the safety of aconite, the decocting period was well regulated by the specification of water volume for decocting at this ancient era. Moreover, the dosages of aconite root and glycyrrhiza in bukuryoshigyakuto (BSGT) formula of “Songban Shanghanlun” are equal to those of shigyakuto (SGT) but the specified water volume to begin decocting is as about twice as that of SGT. When prepared using hard water, BSGT resulted to make the contents of ADA lower and those of non-­ester alkaloids higher compared with those of SGT decoction. It was suggested the spe­cific water volume for each formula prescribed in classical Chinese medicine had considerable significance to determine the dosages of chemical ingredients in the decoctions especially in the circumstances using hard water to prepare them.