Or, to employ a commodity with which, perhaps, you're more familiar it could etch the map of an entire country on a single Lux flake.

10 seconds sound clip from the The 39 Steps (1937) classic radio play.

You can hear this line at 00:41:11 in the radio play.

Quote context

[...]

- We've learned that if you want to make a man talk, send a pretty woman. And when we want to make a woman talk, we make her jealous. Both theories work amazingly well.

- It would appear to me that spying is one activity which provides little or no room for modernization.

- Along with qualifications, I presume that methods have changed little since the days of Moses.

- That's very true. They remain essentially unchanged.

- But there have been radical technical changes in carrying out those essentials.

- For instance, there's a machine, recently developed in this country, so delicate and so accurate that it can etch an invisible secret message on a surface no larger than a grain of corn.

- Or, to employ a commodity with which, perhaps, you're more familiar it could etch the map of an entire country on a single Lux flake.

- And that's probably the finest, thinnest and most fragile thing I can think of for the moment.

- I know that you can read through a flake of Lux, Major. It's actually only two one-thousandths of an inch thick.

- I see. Almost as amazing as this machine I'm speaking of.

- Lux Flakes remind me of women.

[...]