Eugene Volokh is looking for:
... items that match all of the following conditions, and I'd love some help, if any of you would be kind enough to provide. Which items (products or processes) satisfy all these criteria:He lists a few, and here's two of my own: scissors, and the saddle. Scissors were supposedly invented by Leonardo di Vinci, and until the Sarmatians developed the leather saddle in the 4th century AD animals were ridden bareback or with just a blanket.
1. They were unknown to people in ancient Rome circa 150 B.C.
2. They could be manufactured with then-existing technology and then-available raw materials.
3. They would be at least modestly useful in that era.
4. Even a nontechnically minded person today -- say, a smart 12-year-old -- would know how to make and use them.
5. Their absence would be pretty clearly visible.
- Sliced bread (20th century).
- The frisbee (20th century).
- Buttons (13th century).
- The hoisting gear (15th century).
- Copyright (15th century).
- Sliderules (17th century). Most 12-year-olds now can't use one, but my dad could when he was 12.