the notebooks of a doctor/scientist ? who would have had to keep a low profile on his studies in those days - or face the Inquisition? - if in a Catholic ruled country. Otherwise, the above without fear of the powers that be.
Just a research scientist of his day?
The manuscript is too "clean" for it to be a lab journal. There are no corrections, but a scientist wouldn't discard a spoiled page just because of a typo. There are no notes on margins, and those would be very natural when the scientist reviews his notebooks and thinks of something. The manuscript is also split into several chapters, and there is no empty space between them. A scientist would be unlikely to do a study of plants and completely finish it, then switch to something else and be done with it, and so on. A scientist would keep several notebooks, one per study. This looks like a specially arranged material, written for other people to read.