The Doctor's Special Smoking Mixture Sack

A coarse cloth sack belonging to the Third Doctor, filled with a yellowish powdery mixture (including saltpetre, sulphur, fat, and unspecified extras) used as a smoke-decoy. The mixture is stoppered tightly with a drawstring tied in a knot and gives off a lingering acrid sharpness detectable at a distance, suggesting volatility and potential for combustion. Compared to generic knapsacks, this is specifically the Doctor's demonstration sack for the smoking mixture.