Next, head to the center to save. Interacting with the wall on the left will yield Dust.
There are upgrade materials in this direction from the save point; you need to crouch to enter.
After collecting the materials, head up the stairs onto the main path. You can still interact with the wall ahead to obtain Dust.
After interacting with the wall and turning back, you can find the collectible book [Meditations #4: The Posthouse, A Rare Place of Rest] in the pavilion behind you (the first three were available from the start of the game).
