It gets pretty trippy, pretty quick.
As in "We don't have a clear idea what this rune was for, or what it means, but we see it in documents and so added it to Unicode."
This bug will be fixed in Unicode 15.
Documents? I had the strong impression that there are no documents written in runes. A rune we only know by its occurrence in documents would be far more interesting for the existence of a document than it would be for its own sake!
Compare what the page about Anglo-Saxon runes says about the corpus:
> The Old English and Old Frisian Runic Inscriptions database project at the Catholic University of Eichstätt-Ingolstadt, Germany aims at collecting the genuine corpus of Old English inscriptions containing more than two runes in its paper edition, while the electronic edition aims at including both genuine and doubtful inscriptions down to single-rune inscriptions.
> The corpus of the paper edition encompasses about one hundred objects (including stone slabs, stone crosses, bones, rings, brooches, weapons, urns, a writing tablet, tweezers, a sun-dial,[clarification needed] comb, bracteates, caskets, a font, dishes, and graffiti). The database includes, in addition, 16 inscriptions containing a single rune, several runic coins, and 8 cases of dubious runic characters (runelike signs, possible Latin characters, weathered characters). Comprising fewer than 200 inscriptions, the corpus is slightly larger than that of Continental Elder Futhark (about 80 inscriptions, c. 400–700), but slightly smaller than that of the Scandinavian Elder Futhark (about 260 inscriptions, c. 200–800).
So across every runic system we know, we have under 600 texts, all of those texts are short inscriptions, and even to reach that number of samples we need to include texts that we aren't even sure contain any runes.
One of the original goals of Unicode was to be able to computerize every document. I still have some old linguistics books in which characters have been handwritten into typed or even typeset text. So these are the types of documents being referred to: academic papers.
Some fancy books have photographs of ancient writing; I’m not sure if Unicode tries to encode such sources and I pretty much doubt it (how would you even know what to call the symbols? You touch on this in your comment). However often they are attached to treatises that order the characters in some way (I.e. index an alphabet) in which case the first case above would apply.
In other words: thanks to some scholars who wrote down and ordered runic alphabets, you can now discuss runes with your friends and colleagues through email.
That's a weird goal for Unicode to have. We've already accomplished that; a PDF file does the job better (note: PDF documents already support every character existing in the past, present, or future!) while being less complex.
Separately, PDF felt like a step backwards on the day it was announced and sadly nothing since then has changed that.
Of course, that sucks, so I've programmed a nearby key to act as l-ctrl+l-shift+u.
Several characters can also be typed with Compose Key.
For characters I use regularly (in my case, generally the elder and younger futharks), I've created a keyboard out of an Elgato StreamDeck XL so I can type any of these runes with a single button press.
> How do you search for *non-unicode* characters in a pdf document
I guess math has a similar representation in unicode as well.
All that said, I think people use runes to express magic and spells (even to this day). I don’t think all the magical runes are expressed in unicode (and perhaps they shouldn’t). If you want to use a rune in that way, you might have to draw it out in SVG or something and then email it to your friends.
It's an ongoing project. As you seem to have guessed, Unicode math symbols are just about as useless for representing math as Unicode music symbols are for representing music. Producing mathematical documents is done using dedicated software, generally LaTeX.
(And what you get is a PDF, because, as I noted in another comment, PDFs already support every notation there is, was, or ever will be.)
I now have a perverse urge to invent a sculptural writing system just so I can break this completely reasonable claim.
If a clay tablet counts, why not a runestone?
One of the biggest problems in the study of these cultures is that they left no written records. We know they had a writing system, the runes, but as far as we can tell they almost never used it for anything. Quite the opposite is true of Mesopotamian cultures, where we're buried in more records than we have the manpower to translate.
There are. Such documents are called runestones and thousands survive to this day, most in Sweden.
> Documents are also distinguished from "realia", which are three-dimensional objects that would otherwise satisfy the definition of "document" because they memorialize or represent thought; documents are considered more as 2-dimensional representations.
I think "realia" - a term I had never heard before - describes runestones better than "document".
https://en.m.wikipedia.org/wiki/Runic_(Unicode_block)#cite_n...