Do correct me if I'm wrong, but I was under the impression it was explicitly stated to be a creation of Azem in
Days Gone By, Days Yet to Come:
"Oh my, how careless of our Azem."
Thus spoke Hythlodaeus, having ambled into his office at the Bureau of the Architect to find a crystal sitting rather conspicuously on a chair reserved for guests. Slipped from a singularly adventurous pocket, no doubt. He marveled at the way the light played on its facets, like the surface of a tranquil lake, and recalled the first visitor he had received that morning.
In Japanese it's even more blatant with the line:
手のひら大の、澄んだ青色に輝くそれは、朝一番乗りでここを訪れた友人のものに違いない。中に収められているのは本人作の「旅を快適にする道具のイデア、第十四弾」とのことで、その構造について創造物管理局長の立場からアドバイスが欲しいとのことだった。
"In the palm of his hand shimmered with a blue light, a creation of his friend--the first to arrive [in the Bureau of the Architect] that morning. It was an item to make journeying more comfortable*, and they sought out [Hythlodaeus'] advice on the structure."
*Quite literally "the 14th iteration/item" though I'm not sure how to word it naturally in English. It was by no means something Azem perfected immediately, regardless.
(Very rushed translation, please take it with a grain of salt.)