Editing David Singmaster (section)

==Puzzles==
Singmaster had one of the world's largest collections of books on recreational mathematics which he had accumulated starting in the late 1970s.<ref name="allsquared1">{{cite podcast | url= http://aperiodical.com/2013/05/all-squared-number-5-favourite-maths-books-part-1/ | title=All Squared, Number 5: Favourite maths books (part 1) | host=All Squared | website=The Aperiodical | date=11 May 2013 | access-date=25 June 2018 }}</ref> In 1996 he reported that the collection contained over 4700 works.<ref name="list">{{Cite web|url=http://anduin.eldar.org/~problemi/singmast/material.html|title=David Singmaster: List of Available Material|date=1 October 1996|publisher=anduin.eldar.org|archive-url=https://web.archive.org/web/20170309090104/http://anduin.eldar.org/~problemi/singmast/material.html|archive-date=2017-03-09}}</ref> He also collected books on cartoons, humour, and language.<ref name="twisty"/> In 2013 his book collection was reported to be "nearly 10000 items".<ref name="allsquared1"/> Many of the books were housed in a library added as an extension to Singmaster's study.<ref name="allsquared1"/> He had a huge collection of [[mechanical puzzle]]s, which he started in 2002 containing "perhaps 3000 puzzles, of which about 400 are about Rubik's Cube and its variants".<ref name="twisty"/>

From around 1980 to 1982, he ran his own puzzle company, David Singmaster Ltd, which stocked "over 100 puzzles and books".<ref>{{Cite news|title=For Sale|publisher=New Scientist|url=https://books.google.com/books?id=YWj2f6Rir28C&pg=PA395|date=6 May 1982|page=395}}</ref> However the venture lost him "a fair amount of money" and led to prolonged tax negotiations.<ref name="circ78">{{Cite web|author=David Singmaster|title=Cubic Circular Issues 7 & 8|date=1985|url=http://www.jaapsch.net/puzzles/cubic7.htm}}</ref> He referred to this period of his life as "a massive overdose of cubism".<ref name="circ78"/>

Singmaster was both a puzzle historian and a composer of puzzles, and he described himself as a "metagrobologist". Many of his puzzles appeared in publications such as ''[[BBC Focus]]'', ''[[Games & Puzzles]]'', the ''[[Los Angeles Times]]'', and the ''[[The Daily Telegraph|Weekend Telegraph]]''.<ref name="meta">{{Cite web|url=http://books.telegraph.co.uk/Product/David-Singmaster/Problems-For-Metagrobologists-A-Collection-Of-Puzzles-Wit/19147161|title=Problems For Metagrobologists|publisher=Telegraph bookshop|access-date=4 January 2017}}</ref> He published a collection of his puzzles in his 2016 book ''Problems for Metagrobologists''.<ref name="meta"/> From around 2006 Singmaster was a director at the New York-based [[Conjuring Arts Research Center]], retiring from the position (becoming Director Emeritus) in 2013.<ref>[http://conjuringarts.org/about/board-of-directors/ Board of Directors], Conjuring Arts. Retrieved 4 January 2017</ref> He was instrumental in the re-discovery of one of the world's oldest books on puzzles and [[Magic (illusion)|magic illusions]] when he came across a reference to the work in a 19th-century manuscript. The recovered text, ''De viribus quantitatis'' (''{{langx|en|On The Powers Of Numbers}}'') was penned by [[Luca Pacioli]], a Franciscan friar who lived around 1500.<ref>{{Cite news|url=https://www.theguardian.com/world/2007/apr/10/italy.books|title=And that's renaissance magic ...| newspaper=[[The Guardian]] |date=10 April 2007}}</ref>