A guy at the mint had some tricks
For smuggling gold.  He put six
Of the bars up his bum
But got caught (He was dumb.
And so scared that he literally shat bricks).

Based on the suggestion: "The news story about the guy who worked at the Canadian mint, and allegedly smuggled out around C$180,000 worth of gold in his 'internal cavity.'"

To "shit bricks" is a slang term for being so scared or startled that you have this (metaphorical) physical reaction.

I'd likely to smugly claim that I used "literally" correctly in this case.  But while the verb was literal, the noun is actually a lie; they weren't bricks or bars, they were "oreo-sized discs."  When someone updates the slang to "I was so scared I shat an oreo-sized disc!" I'll write a new limerick.