Born in present-day Ghana, Quassi was taken to the Dutch colony of Surinam via the Atlantic slave trade, where he was initially enslaved on a sugar plantation before managing to emancipate himself.

[1] Quassi's roots were among the Kwa speaking Akan people of present-day Ghana, but as a child he was enslaved[2][3] and brought to the New World.

In Suriname, a Dutch colony in South America, he was first put to work in the sugar plantation of New Timotebo.

Quassi participated in the colonial wars against the Saramaka maroons as a scout and negotiator for the Dutch.

[7] One of his remedies was a bitter tea that he used to treat infections by intestinal parasites, this concoction was based on the plant Quassia amara which Carl Linnaeus named after him, as the discoverer of its medicinal properties.