In Canto Three of his poem John Shade (the poet in VN’s novel Pale Fire, 1962) describes IPH (a lay Institute of Preparation for the Hereafter) and calls IPH "a grave in Reason's early spring:"
L'if, lifeless tree! Your great Maybe, Rabelais:
The grand potato. I.P.H., a lay
Institute (I) of Preparation (P)
For the Hereafter (H), or If, as we
Called it - big if! - engaged me for one term