Over time, starting around the reign of Hadrian, inhumation once again became the norm. Eventually, cremation remained a feature of imperial deification funerals, and very few others. The reasons for this shift are not well understood. Some evidence points to Christianity, mystery religions, or influence by the wealthier class in the Roman empire. Individual cremations would have been more costly and time-consuming than inhumations, or mass cremations. Wood for fires was expensive; a well built funeral pyre took time and skill to construct, and consumed a great deal of dry timber. The pyre was built in a shallow pit. Once alight, the pyre must be tended for many hours to ensure that the body was completely consumed. Once the body had been consumed by the fire, the ashes would be sprinkled with wine, placed in an urn and buried either in or next to that spot (in which case the funeral place was a "bustum") or taken elsewhere, in which case the cremation place was known as "ustrina". The smoke of the burning could be sweetened with aromatic herbs, leaves and libations; the elite could use incense. The family had a private meal ("silicernium") at the graveside, then returned home.