From Letters of Thomas Gray, Selected With a Biographical Notice by Henry Milnor Rideout
"It is doubtless an encouragement to continue writing to you, when you tell me you answer with pleasure. I have another reason which would make me very copious, had I anything to say: it is, that I write to you with equal pleasure, though not with equal spirits, nor with like plenty of materials. Please to subtract, then, so much for spirit, and so much for matter; and you will find me, I hope, neither so slow, nor so short, as I might otherwise seem."
From a letter to Horace Walpole, dated January 1747