MAX PLANCK (1858-1947) Autograph letter signed «M. Planck» Berlin-Grunewald, 9 October 1910.

2 pp. 8° gr. bi-leaflet. To a «highly respected Madam President» to cancel a social gathering after the ceremony marking the 100th anniversary of the Friedrich Wilhelm University Berlin: […] I feel impelled to follow up my telephonic words with some written ones, as I would not want you to think me unresponsive and ungrateful to your great kindness. The decision was really difficult for me, but on the other hand I could not get over the fact that this very week marks the first anniversary of the saddest memory of my life [the death of his first wife Marie on 17 October 1909], and that I would therefore make a very bad companion in any case. I consider myself obliged to take part in the official festivities of the anniversary, but I must avoid everything and every social gathering if I do not want to get into unpleasant conflicts. I have promised this to my children, whom I do not want to miss, especially in these days at lunchtime and in the evening. So please accept my heartfelt thanks once again for your kindness and friendliness [...] Max Planck. German theoretical physicist. His work laid the foundations of quantum theory, for which he was awarded the Nobel Prize in Physics in 1918.