Take one ounce of Prussian blue, one-half ounce of oxalic acid; dissolve in one quart of perfectly soft rain water. Insert a quill through the cork of the bluing bottle to prevent waste or putting too much in clothes and you will be pleased with the result. One or two tablespoons of it is sufficient for a tub of water, according to the size of the tub. Chinese blue is the best and costs twelve and a half cents an ounce, and the acid will cost three cents.
from The Ladies' Book of Useful Information, 1896.