RD,
The main parallel rule type of drafting board had a cable running "up" either side and crossing in the middle (making an "X"). The thing is that, were you to run the cables in a "U" shape such that each "edge" had a pair of cables (turned back on themselves with a pulley), you would have an "up" and a "down" at each (vertical) edge. Most normally, you would make that an upside-down "U" to place things where you (most likely) want them. This is the way the (1970's vintage, at least) EnerPac hydraulic presses had their tables move.
On the larger presses, there were two such cable runs. They wrapped around an axle at one side of the main frame such that the runs avoided using more than the cable diameter where it passed the hydraulic cylinder. I helped a friend of mine rebuild such a beastie back in the early-1990's and the hardest part was coming up with the maximum axle diameter that did not wear one out with the torque required to drive it. If you table is 150 lbs and the axle is ø2 inches, then your "drive torque" will be 150 lb-in (12.5 lb-ft) and the table will move 6.28 inches/rev. It seems to me that we ended up somewhere close to ø1.75 on the axle diameter, I just don't remember the weight of the table.
I hope this helps.