A receptacle delivery system for an instrument includes a carriage, a puck supported by the carriage, and a first shelf. The carriage is configured to move from a first location of the instrument to a second location of the instrument. The puck is configured to removably support a receptacle such that a longitudinal axis of the receptacle is substantially coincident with a vertical axis of the puck. The first shelf is positioned at the second location of the instrument and comprises (a) a base extending substantially transverse to the vertical axis of the puck and (b) a first opening defined by the base. When the carriage is positioned at the second location, the longitudinal axis of a receptacle seated in the puck extends through the first opening.