Conrad Gesner was a 16th century Swiss naturalist, bibliographer and probably the first zoologist in the world. His emblematic five-volume masterpiece Historiae Animalium (1551-1558) is an extensive study of the different animals and fantastic creatures known at the time, driven by his own curiosity that later on created a whole new investigative discipline.
The extension of his work is around 3500 pages long, where each species is described under the following criteria: its different names in diverse languages, its habitat, origin, anatomical description, physiology, the potential uses the animal has and its presence in literature or philosophy. It's an incredibly detailed work, one that built the foundations for the naturalists to come such as Darwin and Humboldt- investigators that followed a similar approach to nature studies.
The following illustrations are part of the 1553's published album called Icones Animalium, which contains 611 engravings of mammals, birds, fish and mythological creatures that are considered "monsters" by the author. The execution level of the illustrations is incredible, creating a real precedent for the naturalists to come. It's an extensive catalog of the known animal world of the time and also a reflection of the way the world was conceived back then. Beautiful inspiration material for contemporary designers as well.