Why Keynes is Right

Someone needs to explain why this is wrong... (h/t to Krugsandra for the quote)

If the Treasury were to fill old bottles with banknotes, bury them at suitable depths in disused coalmines which are then filled up to the surface with town rubbish, and leave it to private enterprise on well-tried principles of laissez-faire to dig the notes up again (the right to do so being obtained, of course, by tendering for leases of the note-bearing territory), there need be no more unemployment and, with the help of the repercussions, the real income of the community, and its capital wealth also, would probably become a good deal greater than it actually is. It would, indeed, be more sensible to build houses and the like; but if there are political and practical difficulties in the way of this, the above would be better than nothing.

I'm open to other suggestions to stimulate the economy...  Frankly, I'd rather use the banknotes to build roads, bridges, dams, houses and the like, but if this is what it will take to get things moving again, I say bury the money!