Klein's Protocols in over 8,000 pages recording seminars organized from 1872 to 1913 by Felix Klein and given by Klein, his colleagues, students and other invited speakers, including luminaries such as Hilbert and Minkowski, provide a unique window into our mathematical past. Eugene Chislenko and Yuri Tschinkel have presented a beautiful introduction to the corpus, noting how the breadth of the topics reflect the broad interests and knowledge of Klein (the authors claim that Klein was one of the last three grand mathemagicians able to soar over the full realm of the mathematics of their times, the other two being Hilbert and Poincare).
Klein 's Protocols is huge and handwritten in German, so I thought it would be helpful for aspiring and established mathematicians with an interest in the history of ideas if a listing were available on Math Overflow of some gems in the corpus. Can you make a contribution?
Please provide keywords and page references for any entry. E.g., personally, I would love to have a copy of the figure titled "On regular solids in 4-dimensional space" by W. I. Stringham in Vol. II on pg. 59 (Monday, November 29, 1880).
See also these articles (pages 16-21).