This drawing from Paul Otlet's unpublished Atlas Monde, an attempt to visualize the entire world of knowledge, finishes with an image of the Cellula Mundaneum, or what Otlet conceived to be
“ 'a sort of Sacrarium' located at the core of what he imagined as the pyramidal edifice of the Mundaneum. It represented a " 'synthesis of the World' in the form of an octagonal room where the eight circles of the Atlas Monde are shown in fresco on the walls, surrounded by shelves of books and other smaller pictures. At the center of the room, the eight circles are reproduced on the floor in a circular formation, in the middle of which stands a sculptural representation of the synthesis of syntheses: the sphere “Mundus” supported by the pyramid “Mundaneum.”The Sacrarium, or Cellula Mundaneum, is the end point of what the Mundaneum and the Atlas Monde aimed to achieve: a complete synthesis of knowledge.
"It seems that the model of encyclopedic synthesis as expressed in the drawings of Heymans and Otlet can be retraced to three different spheres of influence: Platonism, positivism, and occultism. First, the use of the pyramid as the symbol for the Mundaneum (and used as the central building in Heymans’s Mundaneum) seems to correspond to the pyramidal model of platonic encyclopedism. In the platonic model, the notion of the encyclopedia referred to the idea that if an individual had completed the path that runs the full circle of the disciplines, he or she was fully educated to engage with the subject of philosophy, which uses all the other disciplines to arrive at an overview of knowledge. In such a platonic model, the full content of the circles of the disciplines is not the ultimate goal but rather the path itself that leads to having a sense of the whole (Morreel, 2006). One can only acquire this sense of the whole if the passage from plurality to unity is completed. This reduction from the many to the one can be achieved, according to Plato, through the method of a dialectic between analysis and synthesis. The analytical synthetic method reduces a mass of knowledge to a set of principles. Dialectics opens the path to the ultimate stage, which is the perception of the unity of all disciplines. This platonic model of encyclopaedism is pyramidal: at the basis there is the mass of phenomena, and at the apex there is a metaphysical understanding of Being. Knowledge must be attained individually by walking the path through the encyclopedic circle. The trajectory through Heymans’s Mundaneum and through the circles in the Atlas Monde may be interpreted as such a “path” that brings the individual reader to a philosophical panorama (the top of the Pyramid of the Mundaneum) from where the unity of knowledge can be grasped (Sphere of the World). Second, the configuration of the Mundaneum and the Atlas Monde evokes the notion of “synthesis” that was central to the nineteenth-century theory of positivism, which incorporated to a certain extent this platonic model of encyclopedism. As Pierre Laffitte, the principal spokesman of French positivism after Auguste Comte’s death, summarized concisely, positivism was a general doctrine providing common and universal rules for the direction of the world, man and society, . . . a doctrine which comprehends all that it is given to us to know, and which in its totality contains parts so well connected and so consonant with each other, and so complete, that nothing is left to chance, no problem is left without solution, and everyone knows in all circumstances what he must think" (Wouter Van Acker, "Architectural Metaphors of Knowledge: The Mundaneum Designs of Maurice Heymans, Paul Otlet, and Le Corbusier," Library Trends, 61 (2012) 371-396, quoting from 384-85).