It can be problematic marking for white on white. I've used some good chalks but they can leave some residue that has to be washed out.
Here are two suggestions:
Lay out the new "Press n' Seal" Glad Wrap over your pattern and trace the design onto it with a permanent viz a viz type marker. (These are made for writing on plastic and bond to the plastic so they shouldn't rub off onto your thread.) Then "stick" it on the quilt and stitch right through it. Tear it away when you've finished. You'll have to get out all of the plastic though, since it carries the marks and if it's left under a stitch it might show.
Another method is to trace the pattern onto bridal tuille with a permanent marker. You can lay the tuile on the quilt, draw over the lines with a chalk pencil and the chalk will go through the fabric and onto the quilt. You will also end up with a permanent copy of the pattern ready to mark again in another block or on another quilt.
How about a fluorescing chalk. (I haven't tried it - just a thought!) You'd have to use a "black light" so you could see it, but it wouldn't be visible in daylight and would also wash out.
Best of luck, Judy Lyon