Artefacts as reminders - a knot in the handkerchief

I few years ago I read Devina's paper titled "Artefacts as designed, artefacts as used: resources for uncovering activity dynamics". On of the participants in the study put papers that needed immediate attention next day on her chair. Next morning, before sitting on a chair she was reminded by papers there, that they need immediate attention.

But how to remind ourself of random, unrelated things. My grandma used to tie knots in her handkerchief. This antique reminding technique has probably fallen out of fashion with paper tissues. There are a few papers available on this subject:

Recently I participated in a heuristic evaluation of an Android app MyCAPP for collecting and studying You Are Here maps. Since I found a map indoors and the GPS signal could not be picked up, I decided to put the phone on a window shelf in a corridor while a was working a few meters away. I really didn't want to forget my phone there so I needed a reminder. I put a cable tie of my laptop power adapter around a handle of a tea cup. When I was leaving I had to tidy up and put the cable in my bag which involved untying the cup and remembering the phone. Simple, elegant and useful.

Recently I had a conversation about this behaviour with a friend and he told me that he often remembers something while already in bed and because he does not want to wake up he picks a random thing and throws it in the middle of the room. In the morning he sees an unusual thing on the floor and remembers whatever he wanted to be reminded of.

Obelix would say: "Human mind is crazy"