It happened that just then Michelangelo passed by and one of them called him over. And Leonardo said: "Michelangelo will explain it to you." It seemed to Michelangelo that Leonardo had said this to mock him. He replied angrily: "You explain it yourself, you who designed a horse to be cast in bronze but couldn't cast it and abandoned it in shame." And having said this, he turned his back on them and left. Leonardo remained there, his face turning red.
The insult had been a pointed one: the technically ambitious equestrian statue that Milan's ruler, Ludovico Sforza, had commissioned from Leonardo had indeed come to nothing. Other anecdotes about the two men's rivalry circulated, so that by the time Giorgio Vasari's groundbreaking "Lives of the Artists" appeared in 1550, the tradition of what Vasari called the sdegno grandissimo (great disdain) between the two was well established.
As well as being competitors they were different enough, indeed, as to be naturally incompatible. Leonardo, the elder of the two by 23 years, was a notable eccentric "[w]ith his coiffed hair and his pink tights and his extravagant wardrobe, his equally finely got-up servants and followers…, his strange sensuality and 'family' of attractive young men." By the early 1500s Leonardo, now in his 50s, found it hard to finish a project and had taken to avoiding commissions so that he could concentrate on scientific research. Michelangelo presented a striking contrast: young, ardent, idealistic. Where the older man was religiously heretical, looking at man as an organism – just one species among many – the younger was a devout, even passionate Christian. Where the older man was cosmopolitan, happy to offer his services to France and even to the Turkish sultan, the younger was a Florentine patriot.