Yes i read about it.
Life was very hard then.
"As canal boats were horse-drawn, the boats had to be
legged through the tunnel – a process where one or more boatmen lay on the cargo and pushed against the roof or walls of the tunnel with their legs. Professional leggers were paid one Shilling and six Pence for working a boat through the tunnel which took one hour and twenty minutes for an empty boat and three hours with a full load."
Their legs must've been like tree trunks. Imagine the dark, damp and lack of fresh air.