Triangle, circle, square:
Also O-Sensei Morihei Ueshiba (1883-1969), founder of Aikido, used those principles to teach his students his concepts and techniques.
In the "Okuden Circle" those three basic principles are firstly thought only on an biomechanics level. They are each by his own but also together a great model to optimize the own body mechanic and techniques.
In the second step you learn the deeper interpretations of those models and their relation to other concepts.