A press assembly is adapted to be used with a disposable stackable cup. According to the preferred embodiment, the press includes a filter. A resilient radially compressible support forms a seal is formed between the filter and the interior of the cup. A detachable rod is mounted to the support. The support is sized to accommodate all radii of the cup. As the user presses down the rod, the press assembly is pushed downward to the bottom of the vessel. The seal maintains continual and firm pressure on the inside surface of the vessel so that the pressurized liquid passes through the filter and the infusion substance is trapped.