This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
The inhalation of fumes of "nitre paper" is often valuable in this malady, and I, with others, strongly recommend it, especially for spasmodic asthma, though it is often available also in the bronchitic form, if congestion be not very acute. The paper may be made with thick blotting-paper, saturating it in a hot solution of nitrate of potash (4 oz. to 1/2 pint), then drying and dividing it as required. In some cases a little of this is sufficient, and a less strength of solution is desirable, but in others relief is not obtained till the room is filled with the vapor (Times, i., 1874, p. 64). Dr. Murrell has recently reported much relief from thick strong papers covered with crystals of nitrate or chlorate; when lighted they give out "dense volumes of smoke" (British Medical Journal, i., 1881). Sometimes, however, especially if there be extensive or active congestion, such treatment proves irritant, and its first use therefore requires watching.