Well, LB, as regards your house idea: Margarete Petersen's text suggests to me that she, like Crowley, may have taken account of geometry -- as 1 is a point, 2 is a line, and 3 is a plane (a triangle) -- one would need to get to 4 to have a solid, hence a house - however as she insists, this card "takes a chance on an opening which the preceding cards have sparked off".
She speaks of sacred space, and suddenly I am reminded that the RWS card - is depicts not only the collaboration of skilled trades (artisan/architect/stone carver - or whatever) -- but it is also the creation of a sacred space
(a cathedral). Mircea Eliade wrote - that sacred space is created in the act of making a space secret -- secret/sacred --- it is the very act of delineating the separateness of the space that makes it sacred.
Originally Posted by FM's translation of MP's text
To enter a new space.
The number three takes a chance on an opening which the preceding numbers have sparked off (loosened).
The wish to to create a space as much for retreat as for encounters, -- a place for new experiences and possibilities; it can also be a place for spiritual and other public gatherings.
From physical workout, Yoga, Massage, a new physical consciousness arises. On the material plane, Commerce. [At the mental level] Ideas and thoughts are solidified. All three planes: physical, social contact, [and mental] discoveries, work together in cooperation.