Cryptonomicon – written by Neal Stephenson, copyright 1999.

Page 147

There is a small chalkboard on the wall of Chatan’s office.  It is a palimpsest, not very well erased; the housekeeping detail here must have a standing order never to clean it, lest something important be lost.  As Waterhouse approaches it, he can see older calculations layered atop each other, fading off into the blackness like transmissions of white light propagating into deep space.

He recognizes Alan’s handwriting all over the place.  It takes a physical effort not to stand there and try to reconstruct Alan’s calculations from the ghosts lingering on the slate.  He draws over them only with reluctance.

Waterhouse slashes an abscissa and an ordinate onto the board, then sweeps out a bell-shaped curve…