《幼学琼林·卷二·老幼寿诞》
晚年才得儿子称为 老蚌生珠 ，头发发白才考中进士称作 龙头属老 。
晚年得子，调之老蚌生珠；暮岁登科，正是龙头属老。
Having a son in old age is called "old clam giving birth to a pearl", and passing the imperial examination at the age of gray hair is called "dragon's head belongs to the old".