When writing last week’s post about the new guidelines for carry-on items, I thought about those “surprise liquids” that can throw off even the most careful traveler.

What do I mean? Did you know a snow globe is governed by the 3-1-1 rules? If you want to carry on a snow globe, the globe part must be no bigger than a tennis ball (about 3.4 ounces of water) and the whole thing, base included, has to fit in a quart-sized baggie.

Peanut butter and yogurt are also governed by the 3-1-1 rule. Grapes, which actually seem more watery than peanut butter, are not.

When there’s any question, consult the TSA’s prohibited items database for guidance.