"Dating from the 15th century, the Aurora consurgens' is a Medieval alchemical treatise. The Aurora consurgens is sometimes attributed to Thomas Aquinas. Unusually, the manuscript contains thirty-eight fine watercolour drawings." quote from wikipedia.
More illustrations from this book can be found here.
Some of my favorites.1 2 3 4 5 6 7
Go to this gallery to see a few more and to read descriptions of each work.