The odor of raisins What would be the use, for instance, in giving the plan of the room that was really my room, in describing the little room at the end of the garret, in saying that from the window, across the indentations of the roofs, one could see the hill. I alone, in my memories of another century, can open the deep cupboard that still retains for me alone that unique odor, the odor of raisins drying on a wicker tray. The odor of raisins! It is an odor that is beyond description, one that it takes a lot of imagination to smell. But I've already said too much. If I said more, the reader, back in his own room, would not open that unique wardrobe, with its unique smell, which is the signature of intimacy. Gaston Bachelard, The Poetics of Space smellmemory
Caustic (optics) Caustics made by the surface of water. In optics, a caustic is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface. The caustic is a curve or surface to which each of the light rays is tangent, defining a boundary of an envelope of rays as a curve of concentrated light. Wikipedia en.wikipedia.org Architectural CausticsCaustic Engineering caustics