Gamow, George. 1966. Thirty Years That Shook Physics: The Story of Quantum Theory.
An excerpt from the book mentioned above:
“Planck was a typical German professor of his time, serious and probably pedantic, but not without a warm human feeling, which is evidenced in his correspondence with Arnold Sommerfeld who, following the work of Niels Bohr, was applying the Quantum Theory to the structure of the atom. Referring to the quantum as Planck’s notion, Sommerfeld in a letter to him wrote:
You cultivate the virgin soil,
Where picking flowers was my only toil.and to this answered Planck:
You picked flowers—well, so have I.
Let them be, then, combined;
Let us exchange our flowers fair,
And in the brightest wreath them bind.”
Who thought these scientists were so poetic!
VISMAYA - History & Philosophy of Physics 