In a scroll known as Rokugei no zu painted in 1847 and now held in the National Diet Library of Japan, there is a fascinating side view of a right whale (Eubalaena japonica) showing the disposition of its internal organs. The importation of Dutch medical texts into Japan led to a new understanding of human internal anatomy and thus new ways of depicting the human body during the Edo period (1603-1868). But how did this study of Western medical texts and illustrations lead to anatomical drawings of whales? Strangely, whale anatomy drawings are the only nonhuman animal anatomical illustrations that remain from early modern Japan, in contrast to the large numbers of animal species whose dissection and vivisection were illustrated in Europe and America. These pictures show some of the ways that curiosity about the workings of the body intersected with the broader curiosity about the natural world and its resources that was an integral part of Japanese natural history (honzōgaku). The conceptualization of whales in these images is just one example of how people in Edo Japan were understood the natural world through observation and personal experience. In this paper, I look at the circulation of knowledge about whales and the types of scholarship that went into producing both anatomical whale images and the more common basic depictions of different whale species. I also consider how scholars' observations could include organisms that were not directly accessible in everyday life through networks of personal and printed communication, and the importance of curiosity about such unusual creatures in the development of natural history.