The Book of Lambspring is one of the best (known) alchemist manuscripts, because of it being simple and direct without to much arcane chemical language, although still symbolic. It's one of the few real-life cases of a centuries-old book on alchemy. Originally published in Latin by Frenchman Nicholas Barnaud under the title "De Lapide Philosophico Triga Chemicum" in Prague, 1599, it does not appear to be an original work, but rather an edited collection of manuscripts that had been passed around for at least twenty years previous. Later, Lucas Jennis published the work in full in Frankfurt, 1625. Though the Christian church burned most of the copies over the centuries, there are still a few copies of the original remaining intact. One of them is in the National Museum of Nurenberg, and another is in the University of Leiden.
It's very short and full of alchemical engravings, so owning a physical copy is worth it, but here it is in PDF via archive.org.
https://ia802902.us.archive.org/31/items/BookOfLambspring/Book%20of%20Lambspring.pdf