Harry Potter and the Goblet of Fire - Chapter Thirty: The Pensieve
A shallow stone basin lay there, with odd carvings around the edge: runes and symbols that Harry did not recognize. The silvery light was coming from the basin’s contents, which were like nothing Harry had ever seen before. He could not tell whether the substance was liquid or gas. It was a bright, whitish silver, and it was moving ceaselessly; the surface of it became ruffled like water beneath wind, and then, like clouds, separated and swirled smoothly. It looked like light made liquid — or like wind made solid — Harry couldn’t make up his mind.