“凡人不可貌相,海水不可斗量”怎么翻译?用英语的直译法翻译

英语相应的俗语是“don't judge a book by its cover” （别以封面而定论一本书的好坏）,不过既然楼主想要的是直译,那么可以参考以下说法：-
1.Never judge a man by his looks,as we could never define the value of an ocean with a tiny
bucket.
2.Clothes and looks do not make the man,a tiny bucket does not suffice to measure the grandeur of the sea.

great minds can not be fathomed，the sea cannot be measured with a bushel --

As a man cannot be known by his looks neither can the sea be fathomed by a gourd.
这是一个约定俗成直译句子！