The picket fence There was a fence with spaces you could look through if you wanted to. An architect who saw this thing stood there one summer evening. Took out the spaces with great care and built a castle in the air. The fence was utterly dumbfounded, each post stood there with nothing round it. Christian Morgenstern, The Art of Looking Sideways www.andrew.cmu.edu spacearchitectureabsurdity
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