a leap in the dark

a leap in the dark

something you do without being certain what will happen as a result I had very little information about the company, so writing to them was a bit of a leap in the dark.
See also: dark, leap
References in classic literature ?
In short, he must have a very contemptible opinion of her capacities, nay, every of her understanding, that, having but one case of her life, shall call that life away at once, and make matrimony, like death, be a leap in the dark.