Thousands of locals and tourists climbed Mount Bromo early Sunday for a lavish religious ceremony that involves throwing ritual offerings into the smouldering crater of an active volcano in Indonesia's tribal hinterlands. Each year people from the Tengger tribe gather from the surrounding highlands to cast fruit, vegetables, flowers, and even livestock such as goats and chickens into Mount Bromo's smoking crater as part of the Yadnya Kasada festival. Other villagers -- not members of the Tengger tribe -- try to catch the offerings before they disappear into the billowing smoke using nets and sarong. This is not technically part of the ritual but reflects local frugal urges not to waste the offerings. The month-long Yadnya Kasada festival harkens back to the 15th century legends of Majapahit kingdom princess Roro Anteng and husband Joko Seger. Unable to bear children after years of marriage, the couple begged the gods for help. Their prayers were answered and they were promised 25 children, as long as they agreed to sacrifice their youngest child by throwing him into Mount Bromo. Legend has it this son willingly jumped into the volcano to guarantee the prosperity of the Tengger people. The sacrifice tradition continues to this day -- though the Tengger sacrifice their harvest and farm animals instead of humans. Dancers in elaborate traditional costumes and tourists were up before dawn to take part in this year's ceremony. Crowds have swelled at Mount Bromo in recent years as the local government promotes the festival as a tourist event. Foreign tourists joined travellers from elsewhere in Indonesia at the mountain's peak, throwing coins into the crater for good luck.