[math-fun] approximating pi by 1

Can anyone help me remember a quote (maybe from Feynman) about approximating pi by 1? I googled "approximate pi by 1", "replace pi by 1", and a few other similar phrases, but didn't find what I'm looking for. (Of course when we're doing dimensional analysis we ignore dimensionless factors like pi, but that's not what I mean; I'm talking about replacing pi by 1 in calculations where getting an answer that's off by just one order of magnitude is good enough.) Thanks, Jim Propp