On the Equilibrium of Planes (Ancient Greek: Περὶ ἐπιπέδων ἱσορροπιῶν, romanized: perí epipédōn isorropiôn) is a treatise by Archimedes in two books. The first book contains a proof of the law of the lever and culminates with propositions on the centre of gravity of the triangle and the trapezium. The second book, which contains ten propositions, examines the centres of gravity of parabolic segments.According to Pappus of Alexandria, Archimedes' work on levers and his understanding of mechanical advantage caused him to say: "Give me a place to stand on, and I will move the Earth" (Ancient Greek: δός μοί ποῦ στῶ καὶ κινῶ τὴν γῆν, romanized: dṓs moi poû stṓ kaí kinô tḗn gên), though other ancient testimonia are ambiguous regarding the context of the saying. Source: Wikipedia (en)