...in his "Letters from the Earth". Sounds like some other place to me...
From the Archangel Satan's letter from the Earth to Archangels Michael and Gabriel, abiding in the Capital-H Heaven: (mods, this is public domain material)
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http://www.positiveatheism.org/hist/twainlfe.htm-----Now then, you have the facts. You know what the human race enjoys and what it doesn't enjoy. It has invented a heaven out of its own head, all by itself: guess what it is like! In fifteen hundred eternities you couldn't do it. The ablest mind known to you or me in fifty million aeons couldn't do it. Very well, I will tell you about it.
1. First of all, I recall to your attention the extraordinary fact with which I began. To wit, that the human being, like the immortals, naturally places sexual intercourse far and away above all other joys -- yet he has left it out of his heaven! The very thought of it excites him; opportunity sets him wild; in this state he will risk life, reputation, everything -- even his queer heaven itself -- to make good that opportunity and ride it to the overwhelming climax. From youth to middle age all men and all women prize copulation above all other pleasures combined, yet it is actually as I have said: it is not in their heaven; prayer takes its place.
They prize it thus highly; yet, like all their so-called "boons," it is a poor thing. At its very best and longest the act is brief beyond imagination -- the imagination of an immortal, I mean. In the matter of repetition the man is limited -- oh, quite beyond immortal conception. We who continue the act and its supremest ecstasies unbroken and without withdrawal for centuries, will never be able to understand or adequately pity the awful poverty of these people in that rich gift which, possessed as we possess it, makes all other possessions trivial and not worth the trouble of invoicing.
2. In man's heaven everybody sings! The man who did not sing on earth sings there; the man who could not sing on earth is able to do it there. The universal singing is not casual, not occasional, not relieved by intervals of quiet; it goes on, all day long, and every day, during a stretch of twelve hours. And everybody stays; whereas in the earth the place would be empty in two hours. The singing is of hymns alone. Nay, it is of one hymn alone. The words are always the same, in number they are only about a dozen, there is no rhyme, there is no poetry: "Hosannah, hosannah, hosannah, Lord God of Sabaoth, 'rah! 'rah! 'rah! siss! -- boom! ... a-a-ah!"
3. Meantime, every person is playing on a harp -- those millions and millions! -- whereas not more than twenty in the thousand of them could play an instrument in the earth, or ever wanted to.
Consider the deafening hurricane of sound -- millions and millions of voices screaming at once and millions and millions of harps gritting their teeth at the same time! I ask you: is it hideous, is it odious, is it horrible?
Consider further: it is a praise service; a service of compliment, of flattery, of adulation! Do you ask who it is that is willing to endure this strange compliment, this insane compliment; and who not only endures it, but likes it, enjoys it, requires if, commands it? Hold your breath!
It is God! This race's god, I mean. He sits on his throne, attended by his four and twenty elders and some other dignitaries pertaining to his court, and looks out over his miles and miles of tempestuous worshipers, and smiles, and purrs, and nods his satisfaction northward, eastward, southward; as quaint and nave a spectacle as has yet been imagined in this universe, I take it.
It is easy to see that the inventor of the heavens did not originate the idea, but copied it from the show-ceremonies of some sorry little sovereign State up in the back settlements of the Orient somewhere.
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