In 1924, Prince Louis de Broglie presented his Ph. D. thesis to the faculty of Paris University. Five years later he was awarded the 1929 Nobel prize in physics for the simple relationship :

Wavelength = planck’s constant / momentum

buried very near the end of the thesis. This equation was credited with giving Erwin Schrodinger the suggestion that led to his developing wave mechanics.
De Broglie’s derivation of that very simple relationship has been “derived” numerous times in textbooks. Often however, there seems to be a mysterious step involved and then the formula pops out like a rabbit from a magician‘s hat. Or, the author just declares that it was a “postulate” which may be the correct way to think of it.
I would like to discuss this and other even more mysterious developments in his thesis that have recently gained attention.