Max Born

“ From that it follows that the motion of a "rigid" body is in general completely determined by one worldline, i.e. by the motion of one point. This result was derived in a very complete and mathematically elegant way by G. Herglotz in his paper "On Bodies that are to be Designated as 'Rigid' from the Standpoint of the Relativity Principle" [3] , and he discussed the exceptional cases at which a larger freedom of motion is present.
Since the new concept of rigidity consequently doesn't contain the necessary 6 degrees of freedom, it certainly cannot be applied to ordinary material rigid bodies. ”

“ In my paper "The theory of the rigid electron in the kinematics of the principle of relativity [1] , I have stated a definition of the "rigid" body satisfying the relativity principle, and I have shown that it suffices to simplify the theory of electrodynamic mass of electrons to a certain extent. In the course of further developing the consequences of this definition, it followed that this "rigid" body in no way is a real analogous to the rigid body of ordinary mechanics in all respects ”

“ Phys. 30, 1, 1909↑ For instance, P. Ehrenfest (this journal, 918, 1909) shows in a very simple manner, that a resting body can never be brought into uniform rotation; I already discussed this fact with A. Einstein at the meeting of natural scientists in Salzburg.↑ G. Herglotz, Ann. ”