In 1913 Einstein is nominated for election to the Prussian Academy of Sciences. Planck feels that he must excuse the nominee for his light-quantum hypothesis:
That he may sometimes have missed the target in his speculations, as for example, in his hypothesis of light quanta, cannot really be held too much against him. At nearly the same time, Einstein writes about Planck’s attempts to derive the radiation formula without light quanta:
Planck’s new theories contain so many hypotheses that they appear almost worthless to me.