That curious book "The Breath of Life" by George Catlin.

In 1861, George Catlin published a classic on mouth breathing titled The Breath of Life which is a contri­bution to the history of medicine, dentistry, and medical anthropology. Catlin, famous for his American Indian paintings and contributions to ethnography, believed that primi­tive Indians were healthier than civilized Europeans because they slept on their backs and breathed through their noses rather than their mouths. He emphasized his point with the use of many rather absurd illustrations. The book had a fair degree of success and was reprinted regularly until 1891. Garrison and Morton list the book as the first published work in America on mouth breathing.