Take, for instance, Professor H. Blits’ 1890 Patented and Improved Methods of Canning Fruits, Vegetables, Etc. The book itself is a gem (in addition to liquor, I’m a fiend for pickling and preserves). In it, Blits includes recipes for curing drunkenness, making candles burn all night, and…the famous soothing syrup. 19th Century babies, apparently, cried for it. Or, given its opium content, one presumes it was more accurate to say that babies cried loudest when it was withheld.
The famous soothing syrup—babies cry for it.
It is perfectly harmless, and very beneficial and good for colic. One pound granulated sugar, one pint of water; let this come to a boil; then boil down 10 minutes more, stirring as little as possible; and one ounce of McMund’s [sic: McMunn’s] elixir of opium and eight drops of annis [sic: anise] oil; when cool, bottle and cork. If you can’t get McMund’s, use one ounce of deodorized tincture of opium instead. The tincture opium in this shape is harmless, as it is very weak; it is not half as strong at the patent soothing syrup now the market. Dose—child one month old, five drops, every hour until relieved; three months old, fifteen drops every hour until relieved; six months old and over, one teaspoonful every hour until relieved.
Given the typos that sound almost right, I'm guessing either Blits or his publisher took down the recipe by ear rather than after much hands-on practice. McMunn's, after all, was a fairly well-known opium elixir.
Twenty drops of this syrup, though, and I bet the patients slept like babies. Precious little junky babies.