The metaphor of the burden basket is based on basket is based on actual baskets Native American women would sling across their shoulders, thus leaving their hands free to work as they collected food, wood and other things for their daily subsistence. At the end of the chores the basket was left at the entry to the home. Visitors, upon entry, were expected to 
leave their burdens and troubles in the basket so the visit was pleasant and happy.
Using a burden basket gives you a physical place to write your burdens, troubles and difficult thoughts down. At the end of a designated period of time of your choice, you can burn the burdens or toss them out to sea to be carried away.
The original burden basket was made of Cedar bark, split and woven in shape of a vessel. The Cedar tree, to some Native Americans, is the tree known to absorb tears, shouts of pain, anger and sorrows. The Cedar tree is also symbolic in healing, cleansing and protection rituals.