Beeswax potted with a lid. Pure and simple.
Beeswax is traditionally used by tailors to strengthen thread when hand sewing buttonholes. Keep it by the sewing machine and pull your thread across it a couple of times before snipping off the thread end, and it will be as easy as pie to get the stiff neat end through the machine needle. It's also great if you're looking to condition and soften the Cocoknits leather cords in the Cocoknits Leather Cord and Needle Stitch Holder Kit or the Cocoknits Leather Cord Set.