The map of the southwest corner of the Pacific Ocean shown here gives directions for the most efficient way to plunder a treasure fleet. The map is a contemporary copy of the now-lost original map drawn up in September 1644 for Governor-General Antonio van Diemen. A zigzag route just above the centre of the map shows the best route to sail to the area east of the Philippines, where the Spanish treasure ships could be attacked and plundered on their way from Acapulco in Mexico to Manila.
In the 16th and 17th century, the treasure fleet was an annual convoy of Spanish ships that transported valuables from Spain’s colonies in the Americas to the Spanish homeland. The treasure fleet is most famous in the Netherlands of course because of the fleet captured by Piet Hein in 1628. Capturing a treasure fleet was very profitable for the Dutch because the valuables helped to finance the war against the Spanish.
Most of the routes taken by the Spanish treasure ships converged near Havana, Cuba, and then continued on to Europe. The route from Mexico to the Philippines was taken less frequently, but the Dutch plundered Spanish treasure there too.
Precise directions are given in the text in the centre of the map:
'Een grondigh onderwijs hoemen alder bequaemst sal cruijssen op het silverschip comende uijt Nova Hispania naer d’Manilha, onse schepen dese voijagie aennemende van hier over Tarnaten, ende uijt Tarnaten de reijse aenvangend in Februarij om met de N:W:Mousson langs de cust van Gilola door de straet Patientie, langs de Cust van Wedde naer de hoeck van Maba door Abel Tasmans passagie langhs de Cust van Nova Guinea, tot dat 50: a 60: mijlen bij oosten d’Eijlanden van de Ladronis ende alsdan sijn Cours N: aen doen tot de hooghte van 14: a 15 graeden doende dan d’Coers west aen, naer de voorgenoemde Eijlanden, ende voorts volgens dese gestijpelde passagie, dese passagie soude mede seer dienstig sijn om vroegh om de Noord tecomen, door de vriese straet ende voorts naer Tartarien.'
Additional directions are included to the left of centre:
'Dese schepen die alhier gaan cruijssen dienden d’Eijlanden vande Philippinas niet naerder te comen als 50: a 60: mijlen, dat door oorsaeck wanneer het silver schip int gesicht creegen datmen het selve d’wal can affsnijden, onder de wal sijnde can sulcx niet wel geschieden, dat door Oorsaeck, dat tegens d’wal can aenloopen, ende het silver can dan wel geberght worden gelijck voor desen wel is gebleecken bij St. Michael ende de Swaen.'
According to the directions, the best time to capture a treasure ship was the first few months of the year during the northwest monsoon season. The Dutch ships were instructed to sail from the northern Moluccas along the north coast of New Guinea to approximately 145 degrees east longitude, then set course for the Marianas (‘Ladrones Islands’), before finally cruising in a westerly direction at a distance of no less than 50 to 60 nautical miles from the east coast of the Philippines.
Unfortunately, the creator of this unusual manuscript map is unknown, but it is known that he worked in Batavia. He used the information recorded by François Visscher in April and May 1643, during the last leg of the first voyage by the famous Abel Jansz. Tasman (1603-1659), as a source for the north coast of New Guinea. It is highly likely that Visscher was involved in the production of the map, possibly with Isaac Gilsemans who was on both of Tasman’s voyages.
Under the text in the centre of the map the following is stated: 'actum Batavia a dij 8:e September A°: 1644, was onderteijckent Abel Tasman'. In other words, it was Tasman himself who signed and approved the map on 8 September 1644. As a result, the map is internationally known as the ‘Tasman map’, but it was definitely not drawn by Tasman.
In the same year – in November 1644 (not the best time of the year according to the directions!) – Maerten Gerritsz. de Vries and François Visscher tried to capture a Spanish treasure ship with a small squadron taking the prescribed route from Batavia. Those on board faithfully followed the directions on the map (or a copy), but their attempt failed miserably. A similar expedition in 1648, led by Tasman himself, did not result in an encounter with the Spanish enemy either…