This
is not really a saying, but the phrase 'lost in the mists of antiquity'
is one that is sometimes used, so I thought I would include it here.
It means
' so old that it cannot be dated', as if we are looking so far back in
time that our view of the past becomes obscured by clouds. I don't
really know how old this bench is, but I think that this is a bit of an
exaggeration!