Spurgeon's quote is legitimate, but it comes from a translation of the 1655 Confession of the Waldenses, chapter XI, as reproduced in Philip Schaff's Creeds of Christendom:
XI. That God saves from this corruption and condemnation those whom he has chosen [from the foundation of the world, not for any foreseen disposition, faith, or holiness in them, but] of his mercy in Jesus Christ his Son; passing by all the rest, according to the irreprehensible reason of his freedom and justice.
This confession was probably written by Jean Leger in the midst of the Piedmont persecution. It is partially an abridgment of the 1559 French Confession, and was brought to England by Samuel Morland. Schaff's English text is based on 19th century translations by William Hazlitt and E. Henderson, but he notes a peculiarity related to the text in brackets above:
The words in brackets are given by Hazlitt and Henderson (perhaps from Morland), but are not found in the French of Leger and Hahn.
So the part of the confession that most clearly indicates a doctrine of unconditional election is apparently not found in the original French version. This is perhaps more surprising because the 1559 French Confession does include similar language:
We believe that from this corruption and general condemnation in which all men are plunged, God, according to his eternal and immutable counsel, calleth those whom he hath chosen by his goodness and mercy alone in our Lord Jesus Christ, without consideration of their works [...]. For the ones are no better than the others, until God discerns them according to his immutable purpose which he has determined in Jesus Christ before the creation of the world.
There are earlier Waldensian Confessions floating around on the internet, such as from 1120 and 1544, but Schaff dismisses them as "partly of doubtful origin, and [having] merely historical interest." In any case, they do not have the language in question either.
So it seems unlikely that we would be able to trace the doctrine of unconditional election back to the Waldensians who preceded the Reformation. The task is especially difficult due to a lack of sources, as Gonzalo L. Pita summarizes:
The documentary scarcity and unconnectedness from which we must
draw the description of Waldensian beliefs is often aggravated by the fact
that the questions, descriptions, and refutations that their opponents
presented were frequently made within a set of theological postulates that
were either taken for granted or just obliterated for the sake of conciseness. ("Waldensian and Catholic Theologies of History", 87)