Wash spinach several times in changes of water until grit free. Cook, covered in just the water that clings to the leaves, until it is tender. Cool and squeeze dry. Mince finely and squeeze dry again. Set flour and salt in food processor and process to combine. Add eggs, oil and spinach and process until combined and begins to form a ball. Add more water, a teaspoon at a time, if dough is too dry. Process 30 seconds. Remove dough from the processor and let it rest, covered with an inverted bowl at room temperature for 1 hour. Set the smooth rollers of a pasta machine at the widest setting. Divide dough into 4 pieces. Flatten 1 piece into a rectangle and cover remaining pieces with an inverted bowl. Dust rectangle with flour and feed it through rollers. Fold rectangle in half, dusting lightly with flour, and feed it through rollers 6 to 8 more times to knead. Fold in half each time and dust with flour, if necessary, so dough does not stick to roller. Turn dial down one notch and feed the dough through the rollers without folding. Turn the dial lower one notch each time until the second to last notch is reached.
Recipe courtesy of Michele Urvater