Common-Place or “Locus Communis” — a place to remember

In this scene from The Merchant of Venice, Shakespeare has the Prince of Arragon, one of Portia’s many suitors, guess which of the three caskets (gold, silver, lead) contains her portrait. Leading the prince to them, Portia says:
Behold, there stand the caskets, noble Prince.If you choose that wherein I am contained,Straight shall our nuptial rites be solemnized.But if you fail, without more speech, my lord,You must be gone from hence immediately.
After contemplating all three, the Prince of Arragon chooses the silver chest:
I will not choose what many men desireBecause I will not jump with common spiritsAnd rank me with the barbarous multitudes.Why then, to thee, thou silver treasure house.Tell me once more what title thou dost bear.“Who chooseth me shall get as much as he deserves.”And well said too—for who shall go aboutTo cozen fortune and be honorableWithout the stamp of merit? Let none presumeTo wear an undeservèd dignity.Oh, that estates, degrees and officesWere not derived corruptly, and that clear honorWere purchased by the merit of the wearer!How many then should cover that stand bare!How many be commanded that command!How much low peasantry would then be gleanedFrom the true seed of honor! And how much honorPicked from the chaff and ruin of the timesTo be new varnished! Well, but to my choice.“Who chooseth me shall get as much as he deserves.”I will assume desert.—Give me a key for this,And instantly unlock my fortunes here.
Opening the casket, he finds not Portia’s portrait, but a picture of a fool’s head and a letter which reads:
“The fire seven times tried this,Seven times tried that judgment is,That did never choose amiss.Some there be that shadows kiss.Such have but a shadow’s bliss.There be fools alive, iwis,Silvered o’er—and so was this.Take what wife you will to bed,I will ever be your head.So be gone. You are sped.Still more fool I shall appear”By the time I linger here.With one fool’s head I came to woo,But I go away with two.—Sweet, adieu. I’ll keep my oathPatiently to bear my wroth.”
— William Shakespeare, The Merchant of Venice, Act II, Scene 9