Johan Isaac Hollandus (late sixteenth Century) is said to have been the two Isaacs Hollandus, father and son, Dutch adepts, who wrote 'De Triplici Ordinari Exiliris et Lapidis Theoria', 'Mineralia Opera Sue de Lapide Philosophico' and other works on Alchemy. The details of their operations on metals may be the most explicit that have been given in writing, and may have been dismissed by some because of this very clarity. John Read, a Professor of Chemistry, in his 'Prelude to Chemistry, an Outline of Alchemy, ' dismisses the writing of the Hollandus pair in a few words, possibly because their clarity of detail led him to suspect a ruse. This is one of the best and most easily understood books on the vegetable work.