Quimby wrote constantly and printed nothing. He left something like ten thousand manuscript pages, kept in the family after his death in 1866, and they did not reach the public until Horatio Dresser edited a selection in 1921. By then New Thought was a movement with congregations, schools and a literature, none of which had been able to read him.
That gap is the whole of the argument about his importance. His patients carried his ideas outward: Warren Felt Evans, a Swedenborgian minister he treated, published books on mental healing from 1869 and was for a time the movement's main theorist; Julius and Annetta Dresser preached his method publicly from the 1880s; and Mary Baker Eddy, treated by him in 1862, went on to found Christian Science. Each of them reworked what they had received, and none of them was working from a text.
The atlas therefore records him as precursor rather than founder, and holds the founding relation to New Thought as debated. A movement with no central authority, no single scripture and several simultaneous origins does not have a founder in the ordinary sense, and every account that gives it one is making an argument about descent that somebody else disputes. What is not disputed is that the people who built it had all, directly or at one remove, been through his consulting room.