Found in "A survey of the cities of London and Westminster: containing the original, antiquity, increase, modern estate and government of those cities." by John Stow (1720) via JISC Historic Books. Roger Crab's grave is at St Dunstan's Church, Stepney, London (in the 'church-yard, south side'):
This Crab, they say, was a Philadelphian, or Sweet Singer.
It is not clear what the cultural reference to 'Philadelphian' or 'Sweet Singer' is. Does anybody know? Perhaps as simple as that he came from Philadelphia (home of the Quakers?)
I think the answer is not too far off... Charles Leslie (1721) in The Theological Works of the Reverend Charles Leslie. In two volumes (accessed via JISC Historic Books) says:
As the Preface to the Snake in the Grafs [grass - s is sometimes 'f'] was employ'd upon the late vile Herefy of Bourignonifm, fent to us from Holland, and a parallel made betwixt that and our Quakerifm, both branches of the fame wild Enthufiafm; fo I thought to have put a Preface to this, upon the fubject of our new Sect of Philedelphians, ftarted up in London fince this Revolution; which is another Graff upon the fame Enthufiaftical Stock, and fo like the Quakers, the fome of them go to the Philadelphian Meetings, and can hardly diftinguifh them from their own.
As the original Philadelphian he names Jane Leade (1624–1704). Another leading name is John Pordage (1607-1681) from Berkshire (where my family lived at that time - who may have changed their name to avoid persecution - but the name change would have been around 1770 ish not as early as the Quaker problem).
I had to ask.. who was Penn in Pennsylvania... William Penn, a Quaker. He saw the disagreement that Charles Leslie expresses in the late 17th Century grow bigger and bigger. The rift between the Quakers and the Anglicans grew. The Quakers were persecuted more and more. William Penn managed to get King Charles II to pay for a mass of land in repayment of a debt in the New Land (America). Originally he called this large piece of land, New Wales. He then changed it to 'Sylvania' (woods and trees)... but Charles changed it to 'Pennsylvania'. William Penn was owner of one of the largest estates in the world (and occupied by a few native Americans and some Dutch). Now had the task of convincing the Quakers of London and Europe to move away from their persecution to the new land... Apparently he convinced the Quakers, Huguenots, Amish, Catholics, Lutherans, Jews (and possibly the Philadelphians). In 1682 he announced the beginning of Philadelphia. Philadelphia comes from Greek, philos (love) and adelphos (brother) to mean Brotherly Love. Penn issued a Charter in 1701 which establish Philadelphia as a city.
I suspected he had taken the name from the 'Philadelphian Society' above... but the Society was apparently named in 1694 'inspired by the Philadelphians in the Book of Revelations.
A bit of a ramble... I cannot find proof that Roger Crab was actually a Philadelphian or Sweet Singer (of Israel) ... perhaps he simply finds himself tarred with the same brush because he is deemed odd.