having nothing to do with Gov. Mark Sanford

I have never hiked the Appalachian Trail. But somewhere I read advice for what "through-hikers" should carry in their backpacks, and I have used this advice to pack for various trips.

The advice, as I recall, is this:

Make three piles of gear:

1. Items you definitely need and cannot do without.
2. Items you might need, but could likely do without.
3. Items you definitely do not need, but would like to have along (e.g., guitar, camera, or frisbee).

Then:

• Take half of the items from the first pile;
• none of the items from the second pile;
• and one item from the third pile.

[Title refers to this. If you know the original source of the advice I recapitulate above, please let me know!]