[gilleain]

From the wiki source (https://content.time.com/time/subscriber/article/0,33009,967...)

> ...has been dividing his time between building the next generation of supercomputers and digging an underground tunnel that starts below his Chippewa Falls house and heads toward the nearby woods. "He's been working at it for some time now," says Rollwagen, who reports that the tunnel is 8 ft. high, 4 ft. wide and lined with 4-by-4 cedar boards. ...

so at that point (1988), it was not yet finished

[atx42]

From the wiki source, my inference is that the tunnel is at least 4 inches long if he was able to line it with 4x4 boards... But aren't 4x4 boards typically called "posts"? I'm amused by how poorly Time reported this.

[codpiece]

We assume inches, but it could be microns.