From Bussy-Rabutin: Le Libertin Puni (by Daniel-Henri Vincent, 2011, pg.70). Vincent never cites his sources so I’m not sure if this is from one of his letters or his memoirs, though I don’t remember it in the memoirs.
[Bussy’s] good friend Jumeaux learned of the news [of his serious illness]. Displaying a moderated optimism, he reminded him of the promise they had made – that the first who died would return to give news of the other world to his comrade. Bussy promised again not to fail, but it was Jumeaux who died soon afterwards from a great debauche. Still one left! Roger, without fear, awaited his visit every evening that followed. Friend Jumeaux did not come. Bussy then concluded with much good sense – and without putting in doubt the good faith of his comrade – ‘that you didn’t always do what you wanted when you were dead.’
Son grand ami Jumeaux prit de ses nouvelles. Faisant prevue d’un optimisme mesure, il lui rappela la promesse qu’ils s’etaient faite, que le premier qui mourrait viendrait donner a son compagnon des nouvelles de l’autre monde. Bussy s’engagea a nouveau a n’y pas manquer, mais c’est Jumeaux qui mourut peu apres d’une grande debauche. Encore une! Roger attendit sa visite, toutes les nuits qui suivirent, sans frayeur. L’ami Jumeaux ne vint pas. Bussy en conclut avec beaucoup de bons sens, et sans mettre en cause la fidelite de son camarade, “qu’on ne faisait pas toujours ce qu’on voulait quand on etait mort.”