I am a Muslim who sometimes attends my local Quaker meeting. In England, Quaker meetings offer unstructured worship where one sits in silence until someone feels moved to speak. In my local meeting I can generally enjoy 30 mins of silent meditation or dhikr until someone speaks. In the silence, Quakers wait on God “as if none were present but the Lord” and the metaphors they commonly use to describe God are spirit and light, which map to the Sufi concepts of ruh and noor.
The ‘Quaker Faith and Practice’ book which sets out the current rules for Quakerism in England says that you need to be “broadly Christian” to be a Quaker (i.e. to be a member of The Religious Society of Friends which is the English Quaker congregation). However, many Quaker meetings (including my local one) make no distinction between members and regular attenders. There is no requirement for an attender to be Christian, as long as one is “in sympathy” with the meeting.
In fact, I have found a number of Quakers to be in sympathy with Sufism. One lady at my local meeting is planning a return trip to Konya after a moving visit. She asked the Sufi brethren who were her guides in Konya to take her to Rumi’s mausoleum but they insisted on taking her to Shams first. Soon after arriving at Shams’ tomb she was overcome by emotion and found herself kneeling on the floor weeping! However, when she was taken to Rumi’s tomb she found it quite ordinary in comparison. When she asked the Sufi brethren why, they asked her “where do you think Rumi is?” In death there is nothing to keep Rumi apart from Shams so Mevlana can be found at the tomb of his friend.