I've decided to test a standard shipping box with a 72 hour heat pack.

I'll be updating photos as the experiment progresses. This is the first photo. The air temperature here, as you can see, is close to 80F. I have given the heat pack just enough time to start to warm, then taped it to the lid of the box. The heat probe is on top of some crumpled newspaper, and beneath another piece of crumpled newspaper, inside of the box (the box is filled with newspaper as though a snake were being shipped, and the probe is where the snake would be sitting). I taped the probe in place so it couldn't shift. The box does have 4 small air holes, as it was a test box, but I covered them with tape for this experiment.

This is a standard Superior shipping box.

Start time: 4 PM.