This recipe is from The White House Cookbook, The Whole Comprising a Comprehensive Cyclopedia of Information for the Home. Published in 1887, the authors are Mrs. F.L. Gillette and Hugo Ziemann, Steward of the White House. I wonder if this was one of Grover Cleveland’s favorites?
For blueberry pickles, old jars which have lost their covers, or whose edges have been broken so that the covers will not fit tightly, serve an excellent purpose as these pickles must not be kept air-tight.
Pick over your berries, using only sound ones; fill your jars or wide-mouthed bottles to within an inch of the top, then pour in molasses enough to settle down into all the spaces; this cannot be done in a moment, as molasses does not run very freely. Only lazy people will feel obliged to stand by and watch its progress. As it settles, pour in more until the berries are covered. Then tie over the top a piece of cotton cloth to keep the flies and other insects out and set away in the preserve closet. Cheap molasses is good enough, and your pickles will soon be "sharp." Wild grapes may be pickled in the same manner.