Its pretty famous in pop culture and you can find alot of references to it all over, for example in Legend of zelda its referenced in two different games
It comes down to somebody dropping a item into a body of water.
And out of the water comes somebody who askes if you droped a golden or silver version of the item.
people are then usually rewarded if they answer honestly.
There are some versions where you don´t like in Tomb raider king
But usually you get something for being honest.