First, the said panel is to be as rich and as big, and as large in each dimension, as the panel that Jacopo di Mariano Borghesi had made, at the altar of the third of the new chapels on the right in San Domenico aforesaid, as one goes toward the high altar. With this addition, that the lunette above the said altarpiece must be at least one-quarter higher than the one the said Jaopo had made. Item, in the middle of the aforementioned panel the figure of St. Barbara is to be painted, sitting in a golden chair and dressed in a robe of crimson brocade. Item, in the said pannel shall be painted two angels flying, showing that they are holding the crown over the head of St. Barnara. Item, on one side of St. Barbara that is on the right, should be painted the figure of St. Catherine the German and on the left the figure of St. Mary Magdalene. Item, in the lunette of the said panel there should be and is to be represented the story of the three Magi, who come from three different roads, and t the end of the three roads these Magi meet together, and go to ogger at the Nativity, with the understanding that the Nativity is to be represented with the Virgin Mary, and her Son, Joseph, the ox and the ass, the way it is customary to do this Nativity. Item, that in the columns of the said panel are to be painted four saints per column, who will be named to the said master Matteo. Item, that in the middle of the predella is to be painted a crucified Christ with the figure of our Lady on one side and St. John on the other, and on either side of this Crucified are to be painted two stories of St. Barbara, and at the foot of the columns of the predella two coats of arms, one on each column, as will be explained to master Matteo. Item, that the said master Matteo has to have this panel of wood made to the measurements mentioned, at his onw expense, and have it painted and adoned with fine gold, and with all the colors, richly, according to the judgement of every good master, like the one of Jacopo Borghesi, and have it set on the altar at his own expense, in eight months from now, without any variance.
Matteo di Giovanni Receives Elaborate Instructions in Creighton E. Gilbert, Italian Art 1400-1500, pp. 38-39