How to weigh a smell
Remember the story of how Walter Raleigh audaciously wowed the Queen's court by 'proving' he could weigh smoke? He took some scales and on them placed an unsmoked cigar, noting its weight. He then smoked the cigar, being careful to tip the ash into the scales as he did so. Voila! The difference between the untouched cigar and the ash was the weight of smoke. At least that's how the story goes.
When departing for my recent trip, my luggage was weighed on a conveyor belt to make sure it didn't exceed the airline's limit. After a few weeks in trains, planes and automobiles, often without much time or facility to wash my clothes, I arrived once again at the airport, ready to depart.
The airline duly weighed my case. It had increased in weight by a not insignificant amount, without any increase in its contents. I can only assume, therefore, that - following Raleigh's famous example - the extra weight could only be attributable to the smell therein.
And that's how to weigh a smell.