From: Philippolis
This Prisoner of War record for Isaac Johannes Van Heerden was transcribed record from various documents held at the National Archives, South Africa, including arrest and shipping information from newspaper sources like De Zuid-Afrikaan.
https://www.gendatabase.com/boer-war-prisoner-record.php?q=655&r=Isaac Johannes&s=Van Heerden&ref=
This set of Prisoner of War documents can be accessed online via the FamilySearch.org project by Clicking Here.