It is my conviction that Carl Kellner had as much to do with the O.T.O. as Rudolf Steiner (or Franz Hartmann or the Hermetic Brotherhood of Light) :
Of course, they both knew Theodor Reuss personally and they shared mutual interest in Yoga, but to render this common interest as the basis for either Steiner or Kellner as ancestors of the O.T.O. is historically unproven.
It was only after Kellner's death in 1905 that Reuss started to develop a study group that was later called O.T.O. — Maybe this group consisted of yoga practitioners of Kellner's private circle, maybe this group was made up by members of the many para-masonic organisations to which both Kellner and Reuss belonged. But all this is in NO WAY evidence of Kellner being either the founder of the O.T.O. or the man who inspired it.
It was 7 years after Kellner's death [!] that Theodor Reuss published that Kellner was the co-founder of the O.T.O.
Tradução portuguesa: Carl Kellner: Jamais um membro de qualquer O.T.O.
On the right: |
Carl Kellner and his original Baphomet of the pre-Ordo Templi Orientis' Inner Triangle
Dr. Carl Kellner: Yoga. Eine Skizze über den psycho-physiologischen Teil der alten indischen Yogalehre. München 1896. [with
handwritten anotations by Oscar Schlag that were the source for many researchers]|
Carl Kellner: Reincarnationen [facsimile of the original handwriting] plus   [transcript of the text]:
Carl Kellner: 16 slokas (third chapter of Patanjali's Yoga-Sutra):
Carl Kellner's Emblem of the Memphis- and Misraim Rite. Here on the cover of Leopold Engel's magazine for the Order of Illuminates
Carl Kellner: Einführung in den Esoterismus unseres Ordens der A. und A. Freimaurer. 
Carl Kellner and Theodor Reuss: Das Geheimnis der Hochgrade unseres Ordens 
Manifesto 33°, 95°, RoseCroix and Johannis Logen 
Short biography on Franz Hartmann
Carl Kellner, Franz Hartmann, Theodor Reuss, Henry Klein: Amtliche Bekanntmachungen. [1903, AASR, MM]
Carl Kellner and Theodor Reuss: Von den Geheimnissen der okkulten Hochgrade unseres Ordens 
Fides Matrimonii / Heiratsurkunde / Marriage Certificate:
Postcards from Carl Kellner to his wife Maria Antoinette Delorme:
Villa Hochwart / Hohe Warte
with the two sphinxes and Eliphas Lévi's Baphomet on the roof gable in Vienna:
Rote Villa in Hallein:
The Rote Villa today:
Carl Kellner very ill:
Carl Kellner's Death Certificate:
Todesanzeigen: Phil. Dr. Carl Kellner:
Der Volksfreund: Funeral of Dr. Karl Kellner.
Der Volksfreund: Obituary and Biography of Dr. Karl Kellner.
Details of Carl Kellner's grave in Hallein:
Franz Hartmann and Emil Adriányi: Br.·.Dr. Carl Kellner
Franz Hartmann: Dr. Karl Kellner, ein Opfer des Okkultismus
From "Noch Mehr Materialien Zum O.T.O."
Biographical notes by Heinz Walter and August Leisler [excerpt]:
Forthcoming: Outlines from the correspondences of Heinz Walter, Bayerische Akademie der Wissenschaften, Georg Schwamberger, Keltenmuseum Hallein, Karl Erwin Lichtenecker
Josef Dvorak: Carl Kellner [without giving sources Dvorak collected the gossips and speculations about Kellner's life, Franz Hartmann, Hatha Yoga and Baphomet]