Another favorite pastime [of Seymour Cray] was digging a tunnel under his home; he attributed the secret of his success to "visits by elves" while he worked in the tunnel: "While I'm digging in the tunnel, the elves will often come to me with solutions to my problem."
I read about it in the "Supermen" book [1], he dug extensive tunnels. Doing repetitive work makes it probably easier to do daydreaming. That's how he designed his Cray super computers architectures in his head.
I honestly think this is a metaphor for a DMT trip. Without getting into too much detail, "machine elves" (http://lmgtfy.com/?q=machine%20elves) are a common name within the culture for beings that give you guidance during the trip.
Another favorite pastime [of Seymour Cray] was digging a tunnel under his home; he attributed the secret of his success to "visits by elves" while he worked in the tunnel: "While I'm digging in the tunnel, the elves will often come to me with solutions to my problem."
https://en.wikipedia.org/wiki/Seymour_Cray#Personal_life