50 litas coin issued to honour the 350th Anniversary of the publication "The Great Art of Artillery" by Kazimieras Semenavicius
 
Kazimierz Siemienowicz (Latin: Casimirus Siemienowicz, Lithuanian: Kazimieras Simonavičius, Belarusian: Казімір Семяновіч, born c. 1600 - c. 1651), was a Polish-Lithuanian general of artillery, gunsmith, military engineer, artillery specialist and pioneer of rocketry. Born in the Grand Duchy of Lithuania, he served the armies of the Polish-Lithuanian Commonwealth, a federation of Poland and the Grand Duchy, and in the armies of Frederick Henry, Prince of Orange, a ruler of the Netherlands. No portrait or detailed biography of him has survived and much of his life is a subject of dispute.

After contributing his expertise to several battles, Siemienowicz published Artis Magnae Artilleriae in 1650. This treatise, which discussed rocketry and pyrotechnics, remained a standard work in those fields for two centuries.

In 1650 Siemienowicz published a notable work, Artis Magnae Artilleriae pars prima (Great Art of Artillery, the First Part). Its name implies a second part, and it is rumored that he wrote its manuscript before his death. It is also rumored that he was killed by members of the metallurgy/gunsmith/pyrotechnics guilds, who were opposed to him publishing a book about their secrets, and that they hid or destroyed the manuscript of the second part. Siemienowicz disparaged what he saw as a culture of secrecy based on "canting Alchymists of the times Past...they dealed in nothing but Smoke, yet arrogantly took upon them to be Professors of so noble and excellent an art as Chymistry."

Artis Magnae Artilleriae pars prima was first printed in Amsterdam in 1650, was translated to French in 1651, German in 1676, English and Dutch in 1729 and Polish in 1963.

In the first part of his work he also wrote that the second one would contain the universal pyrotechnic invention, containing all of our current knowledge. According to his short description, this invention was supposed to greatly ease all measurements and calculations.

For over two centuries this work was used in Europe as a basic artillery manual. Its pyrotechnic formulations were used for over a century. The book provided the standard designs for creating rockets, fireballs, and other pyrotechnic devices. It discussed for the first time the idea of applying a  to artillery. It contains a large chapter on caliber, construction, production and properties of rockets (for both military and civil purposes), including multistage rockets, batteries of rockets, and rockets with delta wing stabilizers (instead of the common ).