Not only were gaps in prosperity much smaller as late as the middle of the eighteenth century, but the rankings which have been so stable since then are not the same when we go further back in history.
Hanging a rose is an ancient Roman custom...The Romans hung a rose over meetings to indicate the meeting was confidential. Attendees understood that whatever was said under the rose -or sub rosa- had to remain a secret.
In an era without telephones or email, anyone wanting to convey private information to someone far away had no option but to write it down and then trust a messenger to carry the letter. Unfortunately, if a messenger suspected the letter might contain valuable information, he could make far more money selling the information to adversaries than he could delivering the letter properly.
Vernet modelled his sleep habits after the Maasai warriors - the African tribe famous for their ability to rise from the deepest sleep to a state of total battle readiness in a matter of seconds.