Bring a medium saucepan of water to a boil. Add the eggs and boil over moderately high heat for 4 minutes. Drain, then rinse the eggs under cool water for 1 minute. Using the back of a spoon, gently crack the eggs all over and peel the shell off. Alternatively, fill a large skillet with enough water to reach two-thirds of the way up the side. Add the vinegar and bring to a simmer. One at a time, crack the eggs into the simmering water and poach until the whites are set but the yolks are still soft, 3 to 4 minutes.