Definition of "dark as Egypt"

Rich[ard]. He muſt have a havvk's eye to ſee the ſtars this evening. VVhy don't you knovv, Jack, it is cloudy out a'doors? / Jack. That's nothing vvith him. He could look through the clouds vvith his glaſs, if it vvas as dark as Egypt, as eaſy as you can look into the other room; or, if he had a mind, he could bruſh avvay the clouds in a trice, vvith that long vvand he carries in his hand.

1797 May, [David] Everett, “The Conjurer, a Dialogue”, in Caleb Bingham, The Columbian Orator: Containing a Variety of Original and Selected Pieces; together with Rules; Calculated to Improve Youth and Others in the Ornamental and Useful Art of Eloquence. […], Boston, Mass.: […] Manning & Loring, for the author, […], for David West, […], and for John West, […], page 175

["][I]t's a long way to the stable, and no one to send." / "I'll go." / "No, indeed; it's past ten, and dark as Egypt. […] I'll rest till Hannah comes, and then do the best I can."

1868, Louisa M[ay] Alcott, “The Laurence Boy”, in Little Women: […], 1st part, Boston, Mass.: Roberts Brothers, published 1869, page 50

His subsequent appointments were: […] 1861–2, Roxbury, where he remarked that the first year was as dark as Egypt, but the second was a time of miracles, financially and spiritually; […]A figurative use.

1869, “Memoirs. Rev. Samuel Tupper.”, in Minutes of the Seventieth Session of the New-England Annual Conference of the Methodist Episcopal Church, Held at Lowell, Mass., March 24–30, 1869. […], Boston, Mass.: James P. Magee, […], pages 39–40

[I]t's as dark as Egypt outdoors. We might go to-morrow if there's a moon.

1911 October, Edith Wharton, chapter V, in Ethan Frome (The Scribner Library; SL8), New York, N.Y.: Charles Scribner’s Sons, page 98

With the Furies at her heels, she bounded down the cellar steps, not even pausing to remember what had once lain at the foot of them. The place was dark as Egypt, but she struck a match, and breathed again.

1937, Dorothy L[eigh] Sayers, “[Prothalamion] Prickly Pear”, in Busman’s Honeymoon: A Love Story with Detective Interruptions, 1st American edition, New York, N.Y.: Harcourt, Brace and Company, page 317

Flashes of lightning lit the canvas walls and air that was hot and suffocating just an hour before was now icy cold. Though only mid-afternoon, it was dark as Egypt.An archaism—the work is set in the 19th century.

2015 March, S[usan] K. Salzer, chapter 4, in Frontier, Pinnacle Books, Kensington Publishing Corp., page 37