It is difficult to date the origins of Shinto, but it predated Buddhism, which was introduced to Japan in the sixth century from Korea. Shintoism gradually enfolded Buddhist beliefs and ceremonies into its own traditions, resulting in a syncretistic religion, a Twofold Shinto. Buddhist deities came to be regarded as manifestations of Japanese deities and Buddhist priests took over most of the Shinto shrines. The centers of worship are the shrines and temples in which the deities are believed to dwell, and believers approach them through torii (gateways). Most important among the shrines is the imperial shrine of the sun goddess at Ise, where state ceremonies were once held in June and December. The Yasukuni shrine of the war dead in Tokyo is also well known. Acts of worship consist of prayers, clapping of hands, acts of purification, and offerings. On feast days processions and performances of music and dancing take place and priests read prayers before the gods in the shrines. In Japanese homes there is a god-shelf, a small wooden shrine that contains the tablets bearing the names of ancestors. Offerings are made and candles lit before it. Shintoism was once a state religion in Japan, but it is now a sect religion, consisting of 13 recognized groups. Most important among them is Tenrikyo in Tenri City (Nara), in which healing by faith plays a central role.