Abstract: A mercury capsule comprises a mercury-filled metal tube, of measured capacity, having closed ends, each of which includes end portions which are cold welded and resistance welded to form an hermetic seal and intermediate portions, which are crimped closed. The length of the intermediate crimped portions of each capsule is designed to permit the mercury within the capsule to expand and stress the lightly crimped portions, during processing operations of a device in which a capsule is mounted, without opening the hermetically sealed end portions of each capsule.The method of the invention comprises filling a metal tube with mercury, closing the open end, and forming light crimps in the tube at spaced locations to form individual capsules, each of which is filled with a measured quantity of mercury.