  A reproducible RCP state is obtained by a well-defined rate process, which is
first-order in free volume, starting from an equilibrium thermodynamic state of
the hard-sphere fluid. The RCP state is also reproduced by a thermodynamic
pathway that inhibits the frequent production of small crystal nucleites which
can lead to heterogeneities at close packing. The simple-cubic single-occupancy
(SCSO) cell system, in which crystallization is de facto prohibited, provides a
reversible path all the way from the ideal gas to the ideal glass (RCP). By
such a route, unique characterization of RCP becomes possible.
