A passively torque-balanced device includes (a) a frame; (b) a drivetrain including a drive actuator mounted to the frame and configured for reciprocating displacement, an input platform configured for displacement by the drive actuator, a plurality of rigid links, including a proximate link and remote links, wherein the rigid links are collectively mounted to the frame, and a plurality of joints joining the rigid links and providing a plurality of non-fully actuated degrees of freedom for displacement of the rigid links, the plurality of joints including a fulcrum joint that is joined both to the input platform and to the proximate rigid link; and (c) at least two end effectors respectively coupled with the remote links and configured for displacement without full actuation.