Crude drugs that feature the name "gui" have appeared in classical medicinal textbooks with different names, and the correspondence between their names and origins remains the subject of research and discussion. In the present study, we investigated these correspondences using the descriptions in the annotations of the Bencaojingjizhu and through our previous study that revealed the standards of weights and measures in this book. Based on this investigation, we strongly speculate that "gui" in the Bencaojingjizhu was the branch skin of Cinnamomum cassia (C. cassia) (corresponding to cinnamon sticks in the market), which fits with the descriptions about the length and weight of "gui" -related crude drugs in this book. We measured the contents of cinnamic