A sketch entitled "Chinese Stone Cutters in Pulau Ubin", showing Chinese <a href="https://en.wikipedia.org/wiki/stone_mason" class="extiw" title="w:stone mason">stonecutters</a> from the "Kay tribe" (that is, of <a href="https://en.wikipedia.org/wiki/Hakka" class="extiw" title="w:Hakka">Hakka</a> origin) at work on <a href="https://en.wikipedia.org/wiki/Pulau_Ubin" class="extiw" title="w:Pulau Ubin">Pulau Ubin</a>, an island off the northeast coast of <a href="https://en.wikipedia.org/wiki/Singapore" class="extiw" title="w:Singapore">Singapore</a>, cutting blocks of stone for the construction of <a href="https://en.wikipedia.org/wiki/Horsburgh_Lighthouse" class="extiw" title="w:Horsburgh Lighthouse">Horsburgh Lighthouse</a> on another island, <a href="https://en.wikipedia.org/wiki/Pedra_Branca,_Singapore" class="extiw" title="w:Pedra Branca, Singapore">Pedra Branca</a>.
<a href="https://en.wikipedia.org/wiki/John_Turnbull_Thomson" class="extiw" title="w:John Turnbull Thomson">John Turnbull Thomson</a> (1821–1884)
John Hall-Jones &amp; Christopher Hooi (1979). <i>An Early Surveyor in Singapore: John Turnbull Thomson in Singapore, 1841–1853</i>. Singapore: <a href="https://en.wikipedia.org/wiki/National_Museum_of_Singapore" class="extiw" title="w:National Museum of Singapore">National Museum</a>, plate 39. <a href="//commons.wikimedia.org/wiki/Special:BookSources/9971917009" title="Special:BookSources/9971917009">ISBN 9971917009</a>.