Buy the fruit when cheap, when not quite ripe; cut off the peels, and roll the fruit in your hand, so as to make them part with the juice readily. Squeeze the juice into a china basin, strain through a muslin which will not allow the least pulp to pass. Have ready 1/4 and 1/2-oz. phials (quite dry), fill with the juice so as to allow 1/2 teaspoonful sweet oil in each. Cork tightly, and set them upright in a cool place. When wanted for use, wind some clean cotton round a skewer, and, dipping it in, the oil will be attracted. The juice will be quite clear; the rinds can be dried for grating.