NetRodent

I've finally met my match. I've been trying unsuccessfully for the last day to find the source of the following quote:

"But who art thou, who lurking in the dark of night, stumbles upon my secret thoughts"

Doing a Google search brings up several pages containing the quote. None of the matches have it used in its original source, they are always used as quotes. Often it appears to be attributed to Shakespeare.

However, I am unable to find it in any of the full-text Shakespeare archives, leading me to think that it may be incorrectly attributed to him.

No luck with Bartlett's Quotations either.

Does anyone know where the above quote comes from or of a potential place to find out?

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"Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats."
--H.L. Mencken