On June 8, 1948, a farmer was pinned under his tractor in an accident in Rosetown, Saskatchewan. He used his pocketknife to scratch this on the fender of the tractor:
The tractor fender was entered into probate and approved as a valid holograph (handwritten) will.
When the courthouse closed sometime ago, the fender and the penknife were tranferred to the custody of the College of Law at the University of Saskatchewan, where it is on display.
Which some time ago triggered an SDMB thread with apparently the most unclear thread title ever, judging from the comments of posters: