For loose tea users, measure tea into a tea ball or a 100-percent-cotton cheesecloth pouch; tie pouch with a string. (Do not use decaffeinated, green or herbal teas.) Place tea in a 2-quart clear glass container.
Bruise rosemary sprigs with the back of a spoon; add to the container. Add water to container; cover. Let stand in sunlight or at room temperature for 2 to 3 hours. (Keep the container away from combustible material. Sunlight coming through glass and liquid can concentrate a beam of light that could start a fire.) Remove tea ball or bags and rosemary sprigs.
Serve sun tea over ice or refrigerate immediately; store up to 24 hours. If desired, serve with sugar and lemon. If desired, garnish each drink with a rosemary sprig. Store in the refrigerator. Makes 5 to 8 (6-ounce) servings.