How big can prominences be?

Quiescent prominences are perhaps the largest entities to occur on the sun in  H-alpha band. The 2010 April 12 example was already detached at its northern end, and would erupt into space some hours later.  In "Secrets of the Sun" Cambridge Uni Press 1984, p96 Ron Giovanelli gives an example, shown in mid-eruption, that may have been about the size of our 2010 prominence, when still attached to the sun.