To the cited seven Chinese correspondences must be added what kind of metal the planets allude to. Futhermore, Sun and Moon should be included and we can reorder the table so the 'planets' follow the order of the days of the week:

Quicksilver is the only liquid (like water) metal. It moves. It is not firm. It is 'quick', as if living. This unique characteristic makes Mercury into a questionable character: Is he really male? The firmness expected of a man is lacking.

Among the seaweeds where the churning sea meets land only the flexible survive. It is necessary to bend and follow the waves. We must find Mercury at the border between 'sea' (winter) and 'land' (summer'). That is his habitat, at equinox.