Objects for throwing to a maximum distance were selected by hefting objects varying in size and weight. Preferred weights increased with size reproducing size-weight illusion scaling between weight and volume. In maximum distance throws, preferred objects were thrown the farthest. Throwing was related to hefting as a smart perceptual mechanism. Two strategies for conveying high kinetic energy to projectiles were investigated by studying the kinematics of hefting light, preferred, and heavy objects. Changes in tendon lengths occurring when objects of varying size were grasped corresponded to changes in stiffness at the wrist. Hefting with preferred objects produced an invariant phase between the wrist and elbow. This result corresponded to an optimal relation at peak kinetic energy for the hefting. A paradigm for the study of perceptual properties was compared to size-weight illusion methodology.A task familiar to many from childhood is that of standing on a beach, in a field, or on a cliff and selecting, by hefting, the stone that can be thrown the farthest distance. Like the perfect skipping stone, the optimal throwing stone evokes an ardent glow of confidence in one's ability to discover and use this appealingly simple, yet distinct tool. What is the optimal throwing stone? Assuming a spherical shape and a fairly homogeneous mass distribution, the relevant object properties are size and weight. What is the appropriate configuration of size and weight and how is it determined? Are people truly able to select from objects varying in size and weight those optimal for throwing to a maximum distance? If so, how?The human perception-action system has been described as a system that temporarily assembles smart, special purpose, deterministic machines over relevant physical properties of the organism and the environment to perform specific tasks