HI Kimmo In continuation of Randy Buth I found one possible related passage in BT Nidda 31a : A preborn child in his mothers womb is like a nut in a cup of water. It is a late babylonian anonimous saying, so I do not know whether if qualifies as relevant materisl. But it could be a proverb and ancient at that, we might never find out. Chana Safrai Jerusalem