Classical mechanics, also known as Newtonian mechanics, was formulated primarily by Sir Isaac Newton in the late 17th century. Newton's work on mechanics is described in his famous book "Philosophiæ Naturalis Principia Mathematica" (Mathematical Principles of Natural Philosophy), commonly referred to as the Principia, published in 1687. In the Principia, Newton laid out the fundamental principles and laws of motion, which form the basis of classical mechanics. These laws include Newton's three laws of motion and the law of universal gravitation. Newton's formulation revolutionized our understanding of motion, explaining the motion of planets, objects on Earth, and other celestial bodies. His work laid the foundation for classical mechanics and set the stage for further developments in physics.