An account circulates of a toggle switch wired into a PDP-10 at the MIT AI Lab, hand-labelled magic and more magic, with one terminal apparently connected to nothing, which nonetheless crashed the machine when flipped. No claim is made here about whether it happened, how it was wired, or why flipping it had any effect.
Editorial judgements on a 0 to 10 scale, argued in the notes below and nowhere else. They order a list. They are not evidence and they never appear in a claim.
Treat an unexplained physical change as a real input until measured, because not connected is a claim about a schematic and not about a circuit.
Triage questions. Who is the first-hand witness and is there an account in their own words rather than a retelling. The story is carried by the Jargon File and by a widely forwarded post attributed to Guy Steele; establish which came first and whether the Jargon File entry is itself the retelling. What is the claimed electrical explanation, and does it survive someone who knows the hardware. Whether any photograph, logbook or machine-room record exists. Note the shape this repository cares about: a story whose charm is that the mechanism is never fully pinned down is exactly the kind that hardens into fact by forwarding.