The gimbal-joint (of inkwell) of Philon (3rd c. B.C.)
It was an exceptional, ahead of its time invention by Philon that is applied today in gyroscopes, navigational instruments and other appliances, etc. It consisted of a cubic box with an opening on each side (for putting an immersible pen at the upper opening). Αn inkwell was mounted at the center of three concentric rings. Each ring was connected to the previous one through diametrically opposed joints. Due to its ingenious design, the inkwell could always be securely stabilised and used regardless of the side facing on top. A similar application of the gimbal of Philon as a navy military mechanism (pithikion) is described by Athenaeus the Mechanic. It was used to automatically keep a sambuca (siege engine) in vertical position while mounted onto a swinging pair of ships in heavy seas.