Landed here to find the “first” revision of a Post. My solution is taken from here: discourse/app/serializers/post_revision_serializer.rb at a0bbc346cb5d5b89d1a3efdfa89869349a8b067f · discourse/discourse · GitHub
PostRevision.where(post_id: 46747).order(:number).to_a
This will give you all raw post revisions including the first.