Here is the famous line 2238 of Unix V6 which is part of some of the most delicate parts of the kernel, context switching.
This comment received huge publicity and just may be the the most famous source code comment in computing history.
2230 /*
2231 * If the new process paused because it was
2232 * swapped out, set the stack level to the last call
3333 * to savu(u_ssav). This means that the return
2235 * actually returns from the last routine which did
2236 * the savu.
2237 *
2238 * You are not expected to understand this.
2239 */
2240 if(rp->p_flag&SSWAP) {
2241 rp->p_flag =& ~SSWAP;
2242 aretu(u.u_ssav);
2243 }
Ref: Unix Sixth Edition Kernel Source Code, � Western Electric Company