Does Anyone Know My John Doe?

My friend found these perfect little (they’re about 1cm wide) seed pods on her garden this week. Each has already shed its’ seed and is now an empty shell ... but from what plant we wondered?

And then we started waxing lyrical on their beautiful shape ... that the plant must have perfected these aerodynamic seed pods to distribute its’ seeds far and wide (which makes me think it’s probably a weed).

So, if you know my John Doe could you please let me know ... before we find a seed pod in tact and start cultivating some sort of triffid ...