When I was in my 20s and 30s, I watched a lot of anime. Slayers, Read or Die, Hyper Police, Chrono Crusade, Maze Mega Burst Space (fantasy mecha), and Tenchi Muyo! were right up there. One of the things that always brought a smile were the paper spells, sigils and writing on paper that could be used to cast magic. Those spells were also fragile and delicate, something that fit well with my idea of artifacts.
So, when I was coming up with the idea of the Farimon Chamber, it made sense to have only a simple, delicate spell be responsible for the creation of the world-altering concept: steam engines.
At their base, a rune is just a shape that is charged with magic. If the material was also delicate, then it would burn itself out and gone forever. But, if a rune was carved into something sturdy, then it could be charged again and again. In effect, creating the holy grail of mage smiths, a durable magical item.