Max Planck was known to the First Doctor as one of the notable scientists living in Berlin in the 1930s. (AUDIO: The Alchemists) Dodo Chaplet recognised his name, despite her lack of knowledge in history. (AUDIO: Fugitive of the Daleks)
In 1911, Planck attended a scientific conference in Brussels, alongside fellow scientists Marie Curie, Albert Einstein, Hendrik Lorentz, Ernest Rutherford. The Robot Doctor planned to use his self-destruct mechanism to destroy them, in order to draw in the real First Doctor, but he was talked down by Vicki Pallister. (AUDIO: Fugitive of the Daleks)
Planck's quantum of action was one of the universal constants. (PROSE: The Secret in Vault 13) A fundamental unit of time to do with light traversing across a distance was known as Planck time. (AUDIO: Interstitial)