Exodus 16:18, 33, 36

When they measured it with an omer, he who had gathered a large amount had no excess, and he who had gathered little had no lack; every man gathered according to his need (family size).

So Moses said to Aaron, “Take a pot and put an omer of manna in it, and place it before the LORD to be kept throughout your generations.”

(Now an omer is the tenth of an ephah.)