From 1922:

Gather the seeds on a dry day, and leave them on a tray for two days. Then put into jars. To every quart of vinegar add one ounce of allspice, one mince of ginger, and a small saltspoonful of salt. Boil the vinegar and spice for ten minutes; allow it to get nearly cold. Then pour over the nasturtium seeds. When cold, tie down tightly.