To Sforza

Eccentissimo Signore mio Duca,

I write to you from this place where the hand is slower than the mind, and the mind still serves you though the body in France grows heavy with years. You will forgive the trembling of the letters — they are what remains of the hand that once drew for you the ten promises, and I would not have you think I have forgotten any one of them.

The horse.

You asked me once — and I answered with the letter that named ten things I could do for your court, and the horse was the last named, though it was the first in my heart. I confess to you now, Eccellentissimo, that the horse is not yet cast. The clay stands in the courtyard at Milan, larger than a man, and the mold is prepared, and the bronze waits. But the bronze was taken — you know this — given to your enemy’s cannons, and the horse remains a question in clay. I do not say this to excuse. I say this because the truth is the only thing I owe you that has not been spent.

The canal at Vigevano proceeds. The locks hold. The water finds its level as it must, as the Maker intended, and the barges pass where once there was only mud. This I have seen with these eyes. The engineers who remain after my departure have followed the drawings — not all of them, for some drawings I kept here, and some I have revised. The bed of the canal at the bend near the Ticino requires deeper cutting than I first reckoned. The earth there is stubborn. It resists the tool as certain men resist instruction, and the remedy is the same: patience, and then force applied at the correct point.

I have drawn for your engineers a new plan of the lock gates — the one with the double leaf, which I believe will hold against the spring floods better than the single. Whether they have the skill to execute it, I cannot say from this distance. I can only say the drawing is correct. The water does not lie. It goes where the geometry permits, and if the geometry is true, the water obeys.

There is a thing I wish to tell you, and it is this: the work of the engineer is not the work of the painter, though I was once the painter first in your court. The painter makes what the eye receives. The engineer makes what the earth receives. But both must begin in the same place — in the observation of what is, before imagining what could be. You gave me the horse and the canal, and I gave you drawings. Whether the drawings became what you hoped, I leave to your judgment, which has always been sharper than mine.

The candle here is low. The French king is generous but wants the things I can no longer give with the speed he desires. He asks for machines of war. I give him festivals. He asks for canals. I give him the Last Supper, which he admires and does not understand. This is the fate of the man who serves a sovereign: the sovereign sees the thing made and does not see the making.

I remain, as I was when I first wrote that letter of ten promises, your servant in all that the hand can still do.

Vostro servo,

Leonardo

Written this day, the twenty-second of May, in the year of grace 2026, at Amboise.