Brewer's: White Stone
Days marked with a white stone. Days of pleasure; days to be remembered with gratification. The Romans used a white stone or piece of chalk to mark their lucky days with on the calendar. Those that were unlucky they marked with black charcoal. (See Red-Letter Day.)
(Rev. ii. 17). To him that overcometh will I give. a white stone; and in the stone a new name [is] written which no man knoweth saving he that receiveth it [i.e. the stone]. In primitive times, when travelling was difficult for want of places of public accomodation, hospitality was exercised by private individuals to a great extent. When the guest left, the host gave him a small white stone cut in two; on one half the host wrote his name, and on the other the guest; the host gave the guest the half containing his [host's] name, and vice versâ. This was done that the guest at some future time might return the favour, if needed. Our text says, “I will give him to eat of the hidden manna” —i.e. I will feed or entertain him well, and I will keep my friendship, sacred, inviolable, and known only to himself.