Pilgrim laughed and said, "You do not know it, but this rod of mine is not the sort of thing the mortal world casually comes by.

凡間, the mortal world, and 等閑, ordinary or casual, together make the point twice. He has been asked a civil question and he is about to answer it with a hundred and seventy characters of verse, which is the most pleased with himself he gets in the chapter.

This rod is:

Three characters, and the fourth verse tag. The others handed over to a landscape, a night and a banquet; this one hands over to an object.

When primal chaos first divided, this iron was smelted; the divine man Yu the Great set it in place with his own hands.

鴻濛 is the undifferentiated vapour before heaven and earth separated — the beginning of everything, and that is when the metal was made. 大禹 is Yu the Great, the sage-king who drained the primordial floods, one of the most solidly canonical figures in Chinese tradition. The rod's history opens at the creation and reaches Yu by the second line.

Lakes and seas, rivers great and small, the shallow together with the deep — with this rod he took the exact measure of them all.

Here is what the thing was actually for. Yu used it as a depth gauge while he was draining the world: you put the rod in the water and read the level. 知之切, knew them precisely, is the technical claim. A survey instrument that later became a weapon is a very good origin for the most famous object in Chinese fiction.