See just above, where Nostromo's pose is "nearly the same" as Decoud's. If Nostromo is sitting in Decoud's pose, then Decoud is the "outcast," reinforcing my notion that it was Decoud's "outcast soul" that possessed Nostromo in the dinghy , rendering him a momentary prey to skepticism.

The pose is specifically tied to Decoud rather than Nostromo by the word "weary," relating back to the first sentence of the previous paragraph.