How is macroscopic superposition demonstrated?

In general, a superposition of states is known through demonstration of interference between the two states: Refraction patterns, positive/negative interference and such.  I want to know how it is done for more macroscopic scenarios. They put a macroscopic object (one visible to the naked eye) into superposition.  It was a sliver of material suspended in some kind of field, and in superposition of vibrating (like a xylophone bar) and just sitting there.

What test was performed on such a system that couldn't be used to determine which of the two states it was in, but nevertheless demonstrated (over the course of multiple iterations of course) a pattern different than what would have been measured if the system was simply in one unknown state or the other, but not in superposition?

The article I originally read on the subject was just based on a press release and did not report such details, but it seems to be the only one that matters. A different scenario will do as well, but firing buckyballs through slits does not count as a sufficiently macroscopic superposition.