Looking for a mixed reality art object as a holiday gift this Cyber Monday? (I know, who isn't?) How about a Hilbert Curve cube, originally created in Second Life by mathematician Henry "Seifert Surface" Segerman, which Henry is now selling on Shapeways, the 3D printing company.
A Hilbert curve is a continuous fractal space-filling curve (hope you know that means, because I actually don't), which Seifert made in SL from 16 sculpty prims, creating the textures with various Python programs, then sent it floating in metaverse space. Now you can buy the physical version for under $25. Added feature: It's made of twisty material, so you can also use it as a hair tie. (I'm sure David Hilbert, who looks quite the 19th century hipster, would approve.)
In his SL heyday, by the way, Henry Segerman created the legendary crooked tesseract house in SL, which I first wrote about in 2006 here, and thanks to a generous donor, still exists in-world: Click here to visit.