When de Broglie in his Nobel Prize Lecture said – among the infinity of motions which an electron ought to have in the atom according to classical concepts, only certain ones were possible, he is referring to: 

the ejected photoelectron from the metal surface

a possible explanation to Maxwell’s objection to Rutherford’s planetary model

Bohr’s idea of stationary orbits in an atom

quantisation of angular momentum of an electron orbiting the nucleus