"They will never know. Once they are dismantled and turned to dust they will get stored away." The little pouch within his robes that also hides his swords will be where he keeps the containers of the poison. As long as no one goes snooping in his belongings then they will never encounter it.

The last thing he needs is the train giving him a hard time for causing problems again. He is going to make sure that everything is prepared perfectly and they don't have a reason to give him a hard time about it.