From Iolanthe, The Nightmare Song:

SONG-LORD CHANCELLOR.
"When you're lying awake with a dismal headache, and repose is taboo'd by anxiety,
I conceive you may use any language you choose to indulge in, without impropriety;
For your brain is on fire - the bedclothes conspire of usual slumber to plunder you:
First your counterpane goes, and uncovers your toes, and your sheet slips demurely from under you..."