The Poetics of Natural History is about the "daydreams" of early American naturalists (from 1730 to 1868) and the collections they created around these dreams. Christoph Irmscher explores how, through the acts of organizing physical artifacts and reflecting upon their collections through writings and images, naturalists from John Bartram to Louis Agassiz were making sense of themselves and their world. These collections allowed them, in a way, to collect themselves.

In the first part of his book, Irmscher offers us a guided tour of the actual collections, beginning in Bartram's disorderly botanical garden in Philadelphia and taking us through the artful display of animals in Charles Wilson Peale's collections and, finally, to the "halls of humbug" of P. T. Barnum's American Museum. The second part of the book moves away from the collections, and explores natural history words and images. Irmscher unforgettably describes American collectors' fascination and horror with the American rattlesnake, and invokes the violent and beautiful world of American birds as described in John James Audubon's paintings and writings. His book ends with a description of Louis Agassiz's 1865 expedition to Brazil as seen through the eyes of the young William James, who reluctantly gathered Brazilian fish while his mentor assembled "proof" that some human beings were less human than others.