Objective To estimate the magnitudes of non-standard volume units of decoction water in herbal prescriptions since the Song dynasty

through data mining of ancient documents on traditional Chinese medicine. Methods Totally 570 ancient books from Northern Song to Qing Dynasty were collected. Based on the included prescriptions

regular expression was used to obtain entries

and the corresponding processing was conducted to generate two data sets. Data set A included prescriptions using the predefined water volume units

while data set B included boiled powder in prescriptions using the predefined water volume units. After data cleaning

the volume of the herbs was converted to the Song dynasty unit using the "units of measurement table of all the Chinese dynasties". Set A was counted by dynasty

decoction water volume

and preparation type

while set B was counted by dynasty

decoction water units

and dosage. The ratio of herbs and water was calculated for items with average value larger than 20. A two-sided 95% confidence interval was expressed

and the number of iterations of 1000 was used. After determining the basic unit of the decoction water

the volume of water in other units was converted based on the ratio of the herb and the water. Results There were five units used for water volume in Song and later dynasties

which were "Zhan（盏）"

"Zhong（钟）"

"Zhong（盅）"

"Wan（碗）"

and "Bei（杯）". Set A included 36423 prescription items while set B included 22249 items. When "Liang（两）" was used as the powder dosage unit

the mean value of the ratio between herb powder and water was 0.37

0.50

0.38

and 0.39 for "Zhan" as the water units in Song

Jin

Ming and Qing Dynasty respectively

and that for "Da Zhan（大盏）" in the Song and Ming dynasty was 0.48 and 0.43 respectively. When "Qian（钱）" was used for powder unit

the ratio was 2.42. 2.73. 2.22

2.51

and 2.56 for water unit of "Zhan" in the Song

Jin

Yuan

Ming

and Qing Dynasty

while that for "Da Zhan" in the Song

Yuan and Ming dynasty was 4.48

2.50. and 3.81; the ratio for "Zhong Zhan（中盏）" and "Xiao Zhan（小盏）" in the Song dynasty were 3.46 and 1.03

while those for the Ming dynasty were 3.21 and 1.19; the ratio for "Zhong（钟）"

"Zhong（盅）"

and "Wan" in the Ming dynasty and Qing Dynasty were 2.56

2.94

3.06

and 2.61

2.89

2.64

respectively. Taking "Zhan" in the Ming Dynasty equal to 300 ml

"Zhan"

"Da Zhan"

"Zhong Zhan" and "Xiao Zhan" in the Song dynasty were estimated to be 289.27 to 293.62 ml

380.29 to 535.36 ml

414.02 ml

and 122.76 ml

while those in the Ming dynasty were 300 ml

335.81 to 455.74 ml

383.40 ml

and 142.17 ml; "Zhan" in the Jin

Yuan and Qing Dynasty was equal to 326.10 to 395.01 ml

265.60 ml

and 304.74-305.73 ml; "Da Zhan" in the Yuan dynasty was 298.57 ml; "Zhong（钟）"

"Zhong（盅）"

and "Wan" in the Ming and Qing Dynasty were 306.14 ml

351.87 ml

365.70 ml

and 311.63 ml

345.86 ml

315.71 ml

respectively. Conclusion "Zhan" as the water unit in the Song

Ming and Qing Dynasty are similar

as well as "Zhong（钟）" in the Ming and Qing Dynasty; "Zhong（盅）" in the Ming and Qing Dynasty are similar

equal to about 15% of "Zhan" in the same dynasty.