To our knowledge, most breed standards don’t make weight a qualifying aspect of a breed, but the Yorkshire Terrier‘s does. A Yorkie “must not exceed 7 pounds.” A compact and well-proportioned stature is an important part of breed “type,” something that wasn’t established right away. We defer to breed experts, but our reading tells us that at early dog shows (as early as 1878), Yorkshire Terriers classes were divided by weight — under 5 pounds and 5 pounds and over (some of those early Yorkies were as much as 12 or 14 pounds). Eventually, exhibitors settled on one class with an average weight of around 7 pounds.
This painting by Renate Diroll is available for purchase here