Kikkerland's Magnetic Hourglass is like any other, except that the sand is replaced with iron filings. This results in eyecatching structures and stalagmite-like prominences forming and collapsing upon the magnetic base. Check out this video they posted to YouTube:
https://www.youtube.com/watch?v=3vErFLDzVFk
It's set for a one-minute countdown, measures six inches tall—a little more with the stand!—and is so lovely I can't even think up one of those weirdly despairing J. Peterman-style catalog descriptions that starts out comically enthusiastic but slowly descends into liminal terror at mankind's savage vicissitude and the imminent failure of the American state and way of life.
$18 and you better like maple.
Magnetic Hourglass [Amazon]