Here's a close up of four small porcelain no-tie insulators made in Girona, Spain by Roses, S.L. a small electrical porcelain company in the mid 1860-1880 timeframe. These no-tie pieces were cemented into the threadless pinholes of porcelain insulators. Two have hollow base openings perhaps to allow easy attachment as a replacement for a broken metal no-tie insulator and two are solid porcelain. I've seen these exact shape and style of insulators made with metalic wires but this is the first example I've ever seen or heard of any made in porcelain. They measure between 3/4"" and 1.5" long.
Note: the pieces look like glass due to the camera flash glare, but are indeed porcelain.