"Every day Grandpa puts on his boots and his warm coat and his fur cap and he goes out into the snowy woods and gathers the sap. With a barrel on a sled, he drives from tree to tree and empties the sap from the buckets into the barrel. Then, he hauls it to a big iron kettle that hangs by a chain from a cross timber between two trees.
"He empties the sap into the iron kettle. There is a big bonfire under the kettle, and the sap boils, and Grandpa watches it carefully. The fire must be hot enough to keep the sap boiling, but not hot enough to make it boil over. "
- Little House in the Big Woods