One theory is that during the [[History of the British canal system|age of the canals]] in Britain, urine would be brought up the canals to the wool mills in Northern England (particularly to Yorkshire), as urine was used in the process of fixing dye to wool. This was particularly the case for the dyeing items blue with [[Indigo dye|indigo]] or more traditionally with [[Isatis tinctoria|woad]], before [[synthetic dyes]] were invented or made commercially available.<ref>{{cite web|url=http://blog.dgwbirch.com/?p=3 |title=Taking the piss |publisher=Blog.dgwbirch.com |date=2009-12-19 |accessdate=2012-03-16}}</ref> Being in the business of transporting urine was much less lucrative than transporting wine, so when the boatmen were questioned what they were carrying they would lie and say "I'm taking wine" and the response would be "No, you're taking the piss" to express disbelief.<ref>{{cite web|url=http://www.history.uk.com/history/a-dyeing-art-jess-dyde/ |title=Dying Art |publisher=History.uk.com |date=2009-02-01 |accessdate=2012-03-16}}</ref> |
One theory is that during the [[History of the British canal system|age of the canals]] in Britain, urine would be brought up the canals to the wool mills in Northern England (particularly to Yorkshire), as urine was used in the process of fixing dye to wool. This was particularly the case for the dyeing items blue with [[Indigo dye|indigo]] or more traditionally with [[Isatis tinctoria|woad]], before [[synthetic dyes]] were invented or made commercially available.<ref>{{cite web|url=http://blog.dgwbirch.com/?p=3 |title=Taking the piss |publisher=Blog.dgwbirch.com |date=2009-12-19 |accessdate=2012-03-16}}</ref> Being in the business of transporting urine was much less lucrative than transporting wine, so when the boatmen were questioned what they were carrying they would lie and say "I'm taking wine" and the response would be "No, you're taking the piss" to express disbelief.<ref>{{cite web|url=http://www.history.uk.com/history/a-dyeing-art-jess-dyde/ |title=Dying Art |publisher=History.uk.com |date=2009-02-01 |accessdate=2012-03-16}}</ref> |