A simple example is given in A Text Book of Inorganic Chemistry, by Anil Kumar De, year 2007, page 383. A more complex example is in The Chemistry of Metal Alkoxides, published by Kluwer Academic Publishers, year 2002, section 9.4 on lead alkoxides, page 115. https://books.google.com/books?id=PpTi_JAx7PgC&dq=massicot&pg=PA383
Mindat with location data http://www.mindat.org/show.php?id=2587&ld=1&pho=
Some comments about the evolution of the definition of the word massicot over the past few centuries is in Lead Manufacturing in Britain: A History, by David John Rowe, year 1983, page 16. The word is in Italian and French in the late medieval era meaning naturally occurring massicot and in some records more vaguely a lead-based ceramics glaze that may or may not have been massicot. https://books.google.com/books?id=ZL4OAAAAQAAJ&dq=massicot&pg=PA16
Archaeomineralogy, by George Robert Rapp, year 2002, page 173, says three lead oxides were known to the ancient Romans: minium, litharge, and massicot. https://books.google.com/books?id=7VMVguiMmY0C&dq=massicot&pg=PA172
Mineral data publishing - PDF http://rruff.geo.arizona.edu/doclib/hom/massicot.pdf