The ipok called "upas" by the Malays and "antiaris toxicaria" by botanists is a tree which supplies a poisonous juice to the Sakais of the plain. It is a colossus of the forest, and belongs to the nettle family.
It has broad, shiny leaves something like those of the magnolia, and numerous species are to be found in the Malay Jungle.
When the season is not too damp and there is a full moon the Sakais make some deep cuts in the bark of this tree and place some bamboo tubes around it in order to catch the sap which flows out abundantly. This juice has a gluey, resinous appearance and is white or yellow according to whether it is extracted from the trunk or from a young bough.
A branch of the poison-tree "Upas".
p. [210].
Then, whilst still in the thick of the forest, they light up a fire and boil the liquid during which process the Alà, who presides over the work, mutters the magical words without which the poison would not have the desired force.
It is not taken from the fire until it presents the aspect of tar, in thickness and colour. Finished to boil, some lemons are squeezed over it and after throwing in red arsenic and other drugs it is all stirred up together and the mixture is ready for use.