http://www.bradshawfoundation.com/thor/balsa-raft.php
Balsa Raft in Aboriginal Navigation of Peru and Ecuador
Extracts from lectures by Thor Heyerdahl
Aboriginal navigation in Peru and adjoining sections of north-western South America is a subject that is little known and still less understood by modern boat builders and anthropologist. The apparent reason is that the Peruvian Indian boat building was based on principles entirely different from those of our ancestry. To the European mind the only seaworthy vessel is one made buoyant by a watertight, air-filled hull, so big and high that it cannot be filled by the waves.
To the ancient Peruvians the only seaworthy craft was one which could never be filled by water because it’s open construction formed no receptacle to retain the invading seas, which washed through. They achieved this by building exceedingly buoyant rafts of Balsa wood.
This type of Peruvian Balsa raft could travel as far as the islands of Polynesia, 4000 miles away. The first record of a Peruvian Balsa raft antedates the actual discovery of the Inca Empire. When Francisco Pizarro left the Panama Isthmus in 1526 on his second voyage of discovery down the Pacific coast of South America; his expedition found Peruvian merchants sailors at sea long before he discovered their country...
Terrific quote and link, thanks.