LR, I remember Piet Hein's grooks with awe. They used to appear regularly in Punch sometime in the mid-60s. For instance:

Just beyond perception's reach
I vaguely seem to see
That life is two locked boxes, each
Wrapped round the other's key.

And yet another from Spike, penned years before greenhouse gases had got on to the agenda:

I saw a woman in Kensington Gore
Take her Rolls-Royce to the grocer's store.
All she bought was a dozen eggs.
When I go shopping, I travel on legs.

This one was accompanied by two sketches labelled WRONG and RIGHT. The first was a cardboard cut-out Roller of the conventionally wheeled variety, the second was another cut-out Roller, but this time fitted with four rotating lags, front and aft.

Can't resist squeezing in just one more from Spike:

As they placed the crown upon his head
Prince Charles turned round and said
"I suppose this means that mummy's dead?"