Weaver's Glasses

"Perhaps You might be interested in a new sword?" asked the merchant with a deep bow while his assistant produced a blade of a dark blueish steel resting on a cushion of white silk from a well-locked chest in a corner of the room. "Darksteel, refined with dust of Melite. And these runes here on the hilt will ensure your enemies are unable to disarm You. Not that you need that, of course. I'm sure Your fighting prowess is more than excellent."
Arathorn Lightblade was sceptical. Darksteel was usually used for shields and arbalests, not swords. Besides, the blade looked a bit unbalanced. He put on his Weaver's Glasses to further inspect the workpiece. As the pattern of the arcane threads became visible, he studied them closely. Then, he found something.
He turned to the merchant. "How much?"

Discovery

Following their vision of a world where everyone can use magic, the Circle of Eyes didn't only standardize the notation of magic in the Codex Arcana but also continued their work in order to share their gift of seeing the Arcane Weave with the rest of the world. After years of theorizing, experimenting with expensive materials and more than one (luckily minor) magical mishap they finally managed to craft a pair of glasses which showed a faint echo of the weave to its wearer.
Those glasses were manufactured 1317 NV by a master runeweaver in Bogholm. Its lenses consisted of extremely thin sheets of Melite in a frame of gold carefully inscribed with runes at specific locations. A fine trace of blueish vapour still emanated from the Melite, obscuring the vision after a few minutes. Aside from that, the glasses worked and all negative effects of the Melite had been taken care of.
The runeweaver who helped to manufacture them was given these first glasses and was immediately able to improve on the quality and precision of his work. The word spread quickly and within only 30 years, every major association of mages or runeweavers owned at least one pair of glasses. Future models also improved on the visibility of the weave as well as the time it takes to manufacture one.

Utility

The advent of Weaver's Glasses revolutionized magic, for the first time allowing the average wizard to see what he is doing when researching new spells. In combination with the Codex Arcana, this induced a change in methodology: Before, inventing a new spell was mostly guesswork. Finding a way to achieve the wanted outcome was hard to do and mishaps were frequent. With the framework for reasoning about which changes to the Weave cause which effects and the Glasse's ability to closely inspect the structure of the Arcane Threads sewn into the objects manipulated, it was now possible to shift the focus from finding a way to do it to finding a way that does not require a grand ritual with 50 or more participants. This lead to a huge leap in what wizards could practically do.
Since then, other uses have emerged: From checking for curses to quality assurance a wide field of magical applications has been found. Some are even nonmagical in nature. Because the Arcane Weave spans every object and defines the laws of physics and similar properties, the analysis of its structure can also find some applications, for example, in biology or metallurgy.

Inventor(s)

The Circle of Eyes

Access & Availability

As a product of Runeweaving, Weaver's Glasses are still rare and expensive, but virtually every association of mages owns at least one pair. Some even lend them to interested non-members.