Hardly do we define the things that are on earth, and the things that are close at hand we find with labour, but the things that are in the heavens, who ever traced out?

Wisdom of Solomon: 9, 16.

Yet it is possible that some bodies, of a nature altogether new, and whose discovery may tend in future to disclose the most important secrets in the universe, may be concealed under the appearance of very minute single stars in no way distinguishable from others of a less interesting character, but by the test of careful and repeated observations.

Introduction (1966 edition)
William Herschel, January 1820.