Query: What was the essential piece Cubist architects explained in their theoretical rules? 
Context: In their theoretical rules, the Cubist architects expressed the requirement of dynamism, which would surmount the matter and calm contained in it, through a creative idea, so that the result would evoke feelings of dynamism and expressive plasticity in the viewer. This should be achieved by shapes derived from pyramids, cubes and prisms, by arrangements and compositions of oblique surfaces, mainly triangular, sculpted facades in protruding crystal-like units, reminiscent of the so-called diamond cut, or even cavernous that are reminiscent of the late Gothic architecture.