A shaker including a vessel and an agitator. The vessel includes a container wall. A rounded bottom closes off the container wall, wherein a border of the bottom is formed radially towards a center axis of the vessel such that the bottom transitions from the container wall to be outwardly domed. An agitator is for use in combination with the vessel, the agitator further comprising a tetrahedral body having four planar faces, four vertices, and six edges, each edge traveling between each of the vertices. Each vertex is rounded off and configured to forcibly contact the container wall and an entirety of the bottom upon shaking the vessel. These rounded vertices create a propeller-like spinning and tumbling motion through the liquid-powder mixture when the vessel is vigorously shaken up and down, and scalloped edges of the agitator produce additional turbulence to efficiently blend a liquid/powder mixture.