According to Noether's Theorem, for every symmetry of the Lagrangian there is a corresponding conservation law, and vice versa. For instance, the invariance of the Lagrangian under time translation and space translation correspond to the conservation laws of energy and momentum, respectively. Also, the invariance of the Lagrangian under rotation in space corresponds to the law of conservation of angular momentum. In classical mechanics at least, there is also a law of conservation of (inertial) mass. What is the corresponding symmetry of the Lagrangian?