The University of Michigan's Special Collections Library has digitized its copy of naturalist John James Audubon's The Viviparous Quadrupeds of North America, originally published between 1845 and 1848. This collection of scans of public-domain material is hi-res, and the library is making the files available for free download and use, with attribution. (Plates from Audubon's more famous Birds of America are also available through the library's website.)
Audubon began working on Quadrupeds when he was 66. The book was a collaborative effort: Rev. John Bachman, a South Carolinian zoologist and Lutheran minister who was a close friend, wrote the text, and Audubon's two sons (who, incidentally, had married Bachman's two daughters) helped with the illustrations. Audubon became ill before the book was finished, and the artist's younger son, John Woodhouse Audubon, ended up executing about half of its plates.
"Because of the difficulty of safely studying wild animals," writes the National Museum of Wildlife Art, "both Audubons often sketched caged or dead animals, causing some of their renderings to appear primitive and sinister." While the older Audubon did make one expedition to observe (and kill and preserve) living animals for this project, the two artists completed many of the observations for the drawings by using specimens preserved or captive, augmenting these with written accounts of animal behavior from explorers who had seen the species in the wild. John Woodhouse Audubon drew these black bears, for example, in the London Zoo.