His bones stood staring through the skin,
By a small cranny forc'd his way
Into a meal-tub: night and day
He fed on the delicious meat.
Grown fat he wanted to retreat,
But found the hole too small by half;
His efforts made a Weasel laugh:
"No, no," he says, "it will not do;
As lean thou cam'st, thou lean must go."
Source: Boothby - Aesop 1.2
M0034 = Perry024. The fable is told about various animals - sometimes a weasel and a fox, sometimes two foxes, or, as here, a mouse and a weasel.