When I shall have fixed in my head the name and the appearance of two or three thousand imperceptible varieties, I shall be well advanced, don't you think so? "The George Sand-Gustave Flaubert Letters" by George Sand, Gustave Flaubert Translated by A.L. McKensie

If we do not take care that imperceptible, steady pressure of the all- surrounding worldliness, which is continually acting on us, will push us right off the foundation without our knowing that we have shifted at all. "The Expositor's Bible: Colossians and Philemon" by Alexander Maclaren

He answered by an imperceptible shrug. "The Fruit of the Tree" by Edith Wharton