One item, everything we know about it, and everything it is connected to.
Words we use: Mystery A question nobody has answered yet. Clue from people Something people wrote down or told long ago: a chronicle, a diary, a story, a carving. Clue from nature Something nature recorded by itself: tree rings, ice, rock layers, or the leftovers of an exploded star. Hunch Our guess that a clue from people and a clue from nature are about the same event. Book or paper Where we read it, so anyone can check our work. Step Something we did, in the order we did it.
The idea: compare unlike records across cultures to find things nobody has lined up. Chose the method with the best track record: a cultural record (chronicle, myth, art) set against a physically anchored one (ice cores, tree rings, DNA, astronomy, geology). Picked sky events in chronicles as the first project and comparative mythology as the second.