More Wodehouse

'Jeeves,' I said that evening -- and I said it coldly -- 'I shall be obliged if you will pop round to the nearest music-shop and procure me a copy of "Sonny Boy". It will now be necessary for me to learn both verse and refrain. Of the trouble and nervous strain which this will involve, I say nothing.' (op. cit., p. 517)

Some cases of praeteritio are inherently (at least, on a strict reading) self-contradictory. This case is different, as the expression is say nothing of X. There would have been real self-contradiction (again, on a strict reading) if Wooster had said this:

'... I'm not even mentioning the trouble and nervous strain which this will involve.'