smooth as glass

*smooth as glass

 and *smooth as silk
Cliché smooth and shiny. (often used to describe calm bodies of water. *Also: as ~.) The bay is as smooth as glass, so we should have a pleasant boat trip. This custard is smooth as silk.
See also: glass, smooth
References in classic literature ?
As you look over the pond westward you are obliged to employ both your hands to defend your eyes against the reflected as well as the true sun, for they are equally bright; and if, between the two, you survey its surface critically, it is literally as smooth as glass, except where the skater insects, at equal intervals scattered over its whole extent, by their motions in the sun produce the finest imaginable sparkle on it, or, perchance, a duck plumes itself, or, as I have said, a swallow skims so low as to touch it.