daf bit: Menachot 76

[cellio]

One ephah = three seahs (dry measure). The omer meal offering consisted of a tenth of an ephah of flour taken from three seahs of barley -- that is, an ephah (three seahs) of barley was reaped, ground, sifted, and resifted to get a tenth of an ephah of fine flour. Why the poor yield? Because this is the new (fresh) harvest and there is more offal and bran in fresh corn than in dry. (So say the rabbis; I have no agricultural experience to draw on.) The two loaves consisted of two tenths taken from three seahs; they're wheat rather than barley, so even though it's also new and not dried, the yield is better. And the showbread consisted of 24 tenths from 24 seahs, the best yield of all, because it was made from old produce. (In all cases this is "fine flour"; I don't know how this compares to yields for ordinary household use where you can be less picky.) (76b)