From the Scottish Institute of Human Relations, Issue 9, December 2002.  The following is from page 14. It is titled Dr Jessie C. B. Sym, 1899 - 2002, ‘ An Appreciation’ by Judith Brearley, and colleagues.
The entire document can be found at: http://www.sihr.org.uk/newsletterarchive/news10.pdf  Bold lettering added.

I find it hard to resist the possibility that Jessie did indeed inherit some of the gifts and qualities of her most famous ancestor. She was extremely proud to be a direct descendant of Dr. Archibald Pitcairn, one of the greatest men in medicine in the late 17th century. He was a true polymath, a poet, playwright and mathematician, friend and physician to Sir Isaac Newton. In 1681 he was a Founding Fellow of the Royal College of Physicians of Edinburgh. As her close friend of 20 years, Dr John Cruikshank, relates:

"A most remarkable coincidence happened to Jessie in the 1980s. She was working in the Rare Book Room of the National Library of Scotland. As it closed she got into conversation with the only other reader, who turned out to be the Chief Librarian of the University of Moscow. He was carrying out research on that very copy of Newton's Principia which had belonged to Jessie's however-many-great-grandfather, a first edition bought by agents of Peter the Great for his new university at St Petersburg, just rediscovered mis-catalogued under Philosophy for two centuries. The marginalia it contained were shown to be Pitcairn's own suggestions to Newton for the second edition!"

Yet again it is clear that in the beginnings of the Scottish Institute can be found a very rich heritage. To have known and worked with Jessie was a rare pleasure and privilege. She was an amazing lady with a great presence and abiding passion for truth.

Grateful acknowledgement to Dr. John Cruikshank for permission to use his accounts of his experience.