Various translations of Tauber have already been posted. Here's the original Polish of the key part.
Original Polish
Sklepienie komory gazowej oparte było na cementowych filarach w środku swej szerokości. Na lewo i na prawo od tych filarów znajdowały się cztery słupy. Zewnętrzną ścianę tych słupów stanowiły kraty z grubego drutu, biegnące aż po sufit i na zewnątrz. Za tą ścianą znajdowała się druga siatka z drobniejszymi oczkami i otworami, a w niej trzecia gęsta. W tej trzeciej siatce poruszało się pudełko, którym wyciągano przy pomocy drutu proszek, z którego wyparował już gaz.
Google Translate
The ceiling of the gas chamber rested upon cement pillars situated in the middle of its width. To the left and right of these pillars stood four columns. The outer face of these columns consisted of grilles made of thick wire, extending all the way to the ceiling and outward. Behind this barrier lay a second mesh with finer openings, and within it, a third, dense mesh. Inside this third mesh moved a small box, used—with the aid of a wire—to extract the powder from which the gas had already evaporated.
GPT Translation
The ceiling of the gas chamber was supported by concrete pillars located along the middle of its width. To the left and right of these pillars there were four columns. The outer wall of these columns consisted of grates made of thick wire, extending up to the ceiling and outward. Behind this wall there was a second mesh with smaller openings, and within it a third, denser one. Inside this third mesh moved a box, by means of which, using a wire, the substance from which the gas had already evaporated was pulled out.
The word translated box or small box is
pudełko which is the diminutive of
pudło (“box”). So some sort of (small) container.
The word powder (which is also used in the Chronicles of Terror translation) seems a bit weird here. The original word is
proszek which seems to mean powder most commonly. Here it seems to refer to the pellets. That does not seem fine enough to say powder in English but perhaps the Polish word is a bit more versatile.