This shawl for mourning wear is from Mlle. Riego's La Mode Winter Book (1862). There were strict customs for mourning, with different garments, fabrics, and quantities of black as well as specific time frames depending on one's relationship to the deceased -- deepest mourning for an immediate family member, "second" mourning for a more distant one, with "half" mourning being the lessening before returning to ordinary dress. (See "Mourning in the 1860s" at Sew Historically and "Stages of (Victorian) Mourning and Fifty Shades of Purple" at Lilac and Bombazine, among others, for examples.)
Mlle. Riego's pattern is for a half-mourning shawl, as mauve, grey, or white were the first colors allowed after the year during which a widow, for example, would wear deepest mourning. An 1860s-era knitter could, of course, knit pretty much any garment in black and call it mourning wear, but this shawl is interesting in that it is designed specifically for that purpose.
All of the patterns in this book except for the mourning shawl are in "tricot écossais," or what we now usually call Tunisian crochet.
Note that the shawl pattern is written using British terms, that is, its treble stitch is equivalent to the American DC -- but it is otherwise very simple, being in what we now call, perhaps because of shawls like this one, "granny stitch".