Simon Stevin (1548–1620) was a Dutch military engineer by profession, but he nurtured a variety of mathematical and scientific insights. Many of these insights were refined in his writings. Mathematically, he is best remembered for his popularization of the decimal notation system and concept. In 1585 he published La Thiende (The Tenth). This work was translated into English and published as Disme by Robert Norton in 1608. The Dutch National Library provides additional information on the various editions and translations of the book.
Stevin began with the necessary definitions, first for whole numbers:
And then for decimals:
A full digitization of the copy owned by the University of California is available at HathiTrust.
Simon Stevin was also an experimental physicist. From his studies of kinetics, he produced De Beghinselen Der Weeghconst (The Principles of Weighing) in 1586.
In analyzing the actions of a directed force, Stevin introduced the concept of a “triangle of forces”.
These images are from the copy owned by the Dibner Library of the Smithsonian Institution Libraries. Rights and reproduction information may be found here.
In Castrametatio Avraico-Nassovica, which was apparently published posthumously in 1631, Stevin wrote on the construction of military camps, including the design and use of barracks and fortifications:
Stevin dedicated his work to the Dutch military leader, Maurice, Prince of Orange (1567–1625).
A full digitization of the copy owned by the New York Public Library is available from GoogleBooks.
Index to Mathematical Treasures