u/Ashjyr

This scene in Ep 4 is Peak Signage Vandalism Literature.

It's when the tree tricks Gu An into going into the ladies.

1. The name of the toilet is Rain-Listening Pavilion.
2. There is some sort of vandalism or notice that reads High Mountain Flowing Water.
3. The writing on left/right walls say "Toilet for me, I for the Toilet", a play on words similar to "All for one, One for all".
4. The poem enclosing the toilet door reads:

Squatting slantingly a big patch

Squatting straightly a single line

Do not squat too high

So it won't wander everywhere