tengwar2

There's still one sea-going paddle steamer: https://en.wikipedia.org/wiki/PS_Waverley.

And possibly human ancestors (https://www.nhm.ac.uk/discover/news/2023/august/human-ancest...)

Something I am interested in is the most ephemeral of technology: maintenance customs. As an example, in my country we have a small number of chalk figures. These are large figures cut in to the landscape, then packed with white chalk to stand out against the grass. Probably the most famous is the White Horse of Uffington (https://en.wikipedia.org/wiki/Uffington_White_Horse), but there are a small number of others such as the Cerne Abbas Giant (https://en.wikipedia.org/wiki/Cerne_Abbas_Giant). Dating them is difficult. The only technique I know of that can be used is optically stimulated luminescence, which was used to put the White Horse at 1380 BC and 550 BC, but by its nature this should be interpreted as "no later than", since it relies on finding material which was exposed to sunlight when the figure was cut and has not been exposed since then. (I worked on the early development of OSL dating, so this is a professional opinion).

The interesting part is that these figures are transitory. If they are not maintained, they disappear - which almost happened to the Long Man of Wilmington (https://en.wikipedia.org/wiki/Long_Man_of_Wilmington). Hence at least for the White Horse, we know that there has been at least an intermittent custom of scouring out the figure and replacing the chalk since prehistoric times up to the present. It's not as neat as a village gathering every seven years to do the job, but there is still a continuity of custom.