A very common application of coupler curves is the generation of approximate straight
lines. Straight-line linkages have been known and used since the time of James Watt in
the 18th century. Many kinematicians such as Watt, Chebyschev, Peaucellier, Kempe,
Evans, and Hoeken (as well as others) over a century ago, developed or discovered either
approximate or exact straight-line linkages, and their names are associated with
those devices to this day.