The breakfast table barometer

Gardeners are notoriously obsessed with the weather, and ways of predicting the weather. That includes me, so I was fascinated when I stumbled over this particular method. It was in a recipe book called Maw Broon's Cookbook, which my husband's daughter Kirsten gave us for Christmas. (If you don't know who Maw Broon is, you'll have to lay your hands on a copy of the Sunday Post, which is a Scottish Sunday newspaper. Oh, OK, Google if you must...) The cookbook is full of traditional Scottish recipes and printed like an old scrapbook, with old newspaper cuttings and vintage advertisements and other bits and pieces pasted in.
Anyway, this particular cutting was headed "The Breakfast Table Barometer". It read: "A cup of hot coffee is an unfailing barometer, if you allow a lump of sugar to drop to the bottom of the cup and watch the air bubbles arise without disturbing the coffee. If the bubbles collect in the middle, the weather will be fine; if they adhere to the cup, forming a ring, it will either rain or snow; and if the bubbles separate without assuming any fixed position, changeable weather may be expected."
I'd never heard of this before. Why coffee? Is it more susceptible than other beverages to barometric pressure? Would the technique work just as well with a cup of tea? Does it matter if you add millk or not? Does anybody know?