Summer Squash Bread & Butter Pickles

1 lbs small yellow squash and/or green zucchini, scrubbed and cut into 1/4-inch-thick rounds 1 onion, cut crosswise into 1/4-inch-thick slices 2 Tbs canning salt 2 c crushed ice 1/2 cup cider vinegar 1/4 cup pure maple syrup (preferably Read on!