On this date in 1947, Thor Heyerdahl‘s raft Kon-Tiki crashed into a reef in French Polynesia (books by this author). The Norwegian ethnologist had set out from Peru the previous April, determined to prove that early South Americans could have traveled across the Pacific and settled in the Polynesian Islands. Heyerdahl and his five-man crew did carry some modern technology, like a radio, navigational equipment, and watches, but the raft itself was made entirely of pre-Columbian materials. The body was made of balsa logs lashed together with hemp ropes, and had gaps between the logs for the water to drain out. The cabin was built of bamboo and had a thatched roof of banana leaves. The mast was made of planks of mangrove, and it held a square sail. It was a replica of the rafts that native Peruvians were using at the time of the first European contact in the early 1500s. Heyerdahl named it after a legendary Incan sun god who was believed to have walked across the Pacific.
In three and a half months, the raft traveled 4,300 nautical miles, weathered two major storms, and proved that Peruvian Incans could have made the voyage themselves. Heyerdahl wrote a book about the adventure, The Kon-Tiki Expedition: By Raft Across the South Seas (1948), and made a documentary film of the same name.