Dave "DJ Flavor Dav" Monroe on Pynchon-l calls attention to this intriguing bit of intertextual and bibliographical play:
McClintic Sphere, in V., p.366:
Keep cool but care.SHROUD, in V., p. 369:
Keep cool but care.B.J. Liddell Hart, Deterrent or Defense: A Fresh Look at the West's Military Position , New York, Prager, 1960:
"Keep strong, if possible. In any case, keep cool. Have unlimited patience. Never corner an opponent, and always assist him to save his face. Put yourself in his shoes--so as to see things through his eyes. Avoid self-righteousness like the devil--nothing is so self-blinding."....as quoted in John F. Kennedy, "Review of B.H. Liddell Hart, Deterrent or Defense," Saturday Review, September 3, 1960, as cited in Averting "The Final Failure": John F. Kennedy and the Secret Cuban Missile Crisis Meetings by Sheldon M. Stern, see p. 40, plus footnote No. 103.
In addition to the tantalizing possibility of a view into the origin of Pynchon's famous epigram, more evidence perhaps of Pynchon's concern with the threat of nuclear war and President Kennedy.
Gravity's Rainbow, p. 65:
Gone away upstream, bas-relief Dumpster lost in the gray light as now Slothrop is going past the sign of Will Stonybloke, of J. Peter PItt, of Jack Kennedy, the ambassador's son--say, where the heck is that Jack tonight, anyway? If anybody could've saved that harp, betcha jack could. Slothrop admires him from a distance--he's athletic, and kind, and one of the most well-liked fellows in Slothrop's class,. Sure is daffy about that history, though. Jack . . . might Jack have kept it from falling, violated gravity somehow? Here, in this passage to the Atlantic, odors of salt, weed, decay washing to him faintly like the sound of breakers, yes it seems Jack might have. For the sake of tunes to be played, millions of possible blues lines, notes to be bent from the official frequencies, bends Slothrop hasn't really the breath to do . . . not yet but someday . . . well at least if (when . . . ) he finds the instrument it'll be well soaked in, a lot easier to play. A hopeful thought to carry with you down the toilet.