Ultimate Marking Pencil™ by Hancy Creations, Inc

The Ultimate Marking Pencil is about to be come your new favourite marking medium! Its white marks show well on dark dark fabrics; it stays on (no smudging!) but washes off... or even better: your iron will erase it! It's a solid form of Pounce Powder formed into that solid by wax, so it won't dry out. The whole "pencil" is a fabric marker; you don't need a refill for it—just use it and sharpen as needed (a sharpener for crayons or eye makeup is perfect for this) until you use it up. Great for marking quilts, or garmentry darts and buttonholes, etc. 
Note: as with all marking tools, test first on a swatch of scrap fabric first to be sure removes cleanly.