I have cobbled together a pinhole camera out of two Amazon.com boxes (one at first, but the image was too small), a piece of paper, a piece of foil, and a lot of packing tape. The test run looks good: The image isn’t that big, maybe 3/8 of an inch, but I was able to see the shapes of clouds as they drifted in front of the disc, so it should be sharp enough to show the eclipse.
Since I was building it around the same time of day that the eclipse will be happening, now I know what the sightlines are going to be like. I’ll definitely have to go somewhere less obstructed, probably somewhere higher in case the clouds roll in tomorrow. Update: I did.