After Dürer finished his apprenticeship with Wolegmut at the age of 19, he followed the tradition of young artists and embarked on a guild tour of southern Germany to study the work of various artists and printmakers. He was probably in Strasbourg when he painted his "Portrait of the Artist holding a Thistle" in 1493. He was 22 years old. The portrait was painted in oil on vellum, and was pasted on canvas several centuries later. Johann Wofgang von Goethe saw the painting in 1805 at a museum in Leipzig and was deeply impressed. In 1922 it was purchased by the Louvre.
"The face still has some of the childish features seen in his early drawing of a Self Portrait," says the Louvre Web site, "but the manly neck, the strong nose, and the vigorous hands are already those of an adult. Dürer, who was also an excellent engraver, composed his works in a very graphic fashion. The almost metallic fineness of detail, seen in the prickles of the thistle, also recalls his early training as a goldsmith."
There are two competing theories about the meaning of the painting. Some scholars believe it was an engagement present for Agnes Frey, whom Dürer would marry the following year. "In fact," says the Louvre, "the thistle held by the artist is called 'Mannstreu' in German, which also means 'husband's fidelity.' This pledge of love would also explain the elegance of the costume. The main loophole in this hypothesis is that Dürer may still have been unaware of the marriage, which had been arranged by his father." A rival theory is that the thistle represents the crown of thorns from Christ's Passion. In any case, the artist's inscription reads, "Things happen to me as it is written on high."
(http://www.openculture.com/2013/07/the_genius_of_albrecht_durer_revealed_in_four_self-portraits.html)