In a mass of large bubbles The froth, therefore, though lacking long-range symmetry, nevertheless has very definite rules as to its composition. It is pleasing in appearance because the eye senses this interplay between regularity and irregularity. Structure, Substructure, and Superstructure symmetry
We wonder which is real, he of the picture or he who talks? In the tea room the fear of repetition is a constant presence. The various objects for the decoration of a room should be so selected that no color or design shall be repeated. If you have a living flower, a painting of flowers is not allowable. If you are using a round kettle, the water pitcher should be angular. A cup with a black glaze should not be associated with a tea-caddy of black lacquer. In placing a vase or an incense burner on the tokonoma, care should be taken not to put it in the exact center, lest it divide the space into equal halves. The pillar of the tokonoma should be of a different kind of wood from the other pillars, in order to break any suggestion of monotony in the room. Here again the Japanese method of interior decoration differs from that of the Occident, where we see objects arrayed symmetrically on mantelpieces and elsewhere. In Western houses we are often confronted with what appears to us useless reiteration. We find it trying to talk to a man while his full-length portrait stares at us from behind his back. We wonder which is real, he of the picture or he who talks, and feel a curious conviction that one of them must be fraud. Okakura Kakuzō, The Book of Tea repetitionsymmetry
Materials and how to employ them Forming a paper clip presents a common dilemma encountered by engineers and inventors: the very properties of the material that make it possible to be shaped into a useful object also limit its use. If one were to try and make a paper clip out of wire that stayed bent too easily, it would have little spring and not hold papers very tightly. On the other hand, if one were to use wire that did not stay bent, then the clip could not even be formed. Thus, understanding the fundamental behavior of materials and how to employ them to advantage is often a principle reason that something as seemingly simple as a paper clip cannot be developed sooner than it is. Henry Petroski, The Evolution of Useful Things Ideas behind their time material