In 1650 Mizar was the first double one of these discovered; today we know it's actually a quadruple
Recent studies indicate that 
the Alcor binary and Mizar quadruple are somewhat closer together than 
previously... [DOC] [TLE] A New View Of Mizar [PAR] Everything you wanted to know about the most well-known double star and two ... 
to have split Mizar  as the first double star ever discovered  around 1650.