Original historical works on science and technology
Antiquarian science books are original historical works (e.g., books or technical papers) concerning science, mathematics and sometimes engineering. These books are important primary references for the study of the history of science and technology, they can provide valuable insights into the historical development of the various fields of scientific inquiry (History of science, History of mathematics, etc.)
The landmark are significant first (or early) editions typically worth hundreds or thousands of dollars (prices may vary widely based on condition, etc.). 
Reprints of these books are often available, for example from Great Books of the Western World, Dover Publications or Google Books.
Incunabula are extremely rare and valuable, but as the "scientific revolution" is only taken to have started around the 1540s, such works of Renaissance literature (including alchemy, Renaissance magic, etc.) are not usually included under the notion of "scientific" literature. Printed originals of the beginning scientific revolution thus date to the 1540s or later, notably beginning with the original publication of Copernican heliocentrism. Nicolaus Copernicus' "De revolutionibus orbium coelestium" of 1543 sold for more than US$2 million at auctions.
References.
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