Describe the "water treatment" Aunt Polly used on Tom as part of her home remedies.

From the text:

She had him out at daylight every morning, stood him up in the wood-shed and drowned him with a deluge of cold water; then she scrubbed him down with a towel like a file, and so brought him to; then she rolled him up in a wet sheet and put him away under blankets till she sweated his soul clean and “the yellow stains of it came through his pores”—as Tom said.