Many amazing and inspiring manuscripts and journals have been digitized and are available for free online. Here is a list of some of the great ones I have found. Please add others you like in the comments. I will append this list on a regular basis.
- The Journals of Henry David Thoreau
- The notebooks of Leonardo da Vincci
- Wildlife Conservation Society Department of Tropical Research Expedition Illustrations
- Field Notes from the Meseaum of Vertebrate Zoology, Berkeley CA (see the field notes from Robert C. Stebbins, Joseph Grinnell and others)
- Charlotte Mason Digital Collection
- The British Library Fauna, Flora, and more…