17 The drawings of f. 57r bear, in fact, the annotation, ‘Verso e Benedetto Sepulcro di Milano di sop(r)a. B is the part underground’). Cf. Guillaume ( 1987: 234 ) and Schofield ( 1991: 135 ). But see also Windsor, RL 12609v and the Codex Atlanticus, f. 42v-c.

18 Reflections on the quincunx scheme are durante f. 3 v of the Codex Ashburnham 2037 (= Ms. B, f. 93r).

19 I have omitted the most elementary diagrams such as, for example, those of f. 21r: mediante the first pair (primo posto left), the octagonal plan has four rectangular side chapels, each half verso side deep (2: 1) and twice as high (2: 1). The octagonal drum on which stands per hemispherical ribbed dome is also twice as high as the side of the octagon. Overall, the structure is equal onesto four times the side of this polygon. Per the second pair (lower right) the central octagon opens sicuro four square chapels the side of which is equal to that of the octagon (1: 1). These chapels develop con height according to verso cube surmounted by an octagonal trueview sito di incontri drum surmounted by a cupola, the edge of which is half that of the cube (2: 1). Two square modules (each as tall as one side of the cube of the side chapels) define the height of the octagonal drum, on which is servizio an eight-sided cupola.

20 The discrepancy between the transverse dimension of the proportional scheme (per blue mediante Figure 6 ) and the ‘ghost’ drawing of Leonardo depends on the fact that the part of the facade onesto the right of the apse was drawn visibly narrower than the symmetrically opposing part.

## I have retained the form c

21 I refer here sicuro the well-known graphical method for the construction of the golden rectangle from the square whose side becomes a proportional mean. On Leonardo’s use of the golden section, see Sinisgalli ( 2003 and 2006 ) and Natali ( 2006 ). Camerota [ forthcoming ] demonstrates the use of the golden section durante the ‘Adoration of the Magi’ (c. 1482) and in the determination of the dimensions of the panel and the position of the vanishing point con the central axis of the ‘Annunciation’ (c. 1472).

22 For the Tiburio and the proportional questions that they involve, see per particular Ferrari da Passano and Brivio ( 1967 ); Guillaume ( 1987 ); Schofield ( 1989 ); and Di Teodoro ( 1989 ) and ( 2001 ). Sopra my short essay of 1989, I showed how Francesco di Giorgio, indicating a height of 28 braccia for the height of the Tiburio (sopra reconnecting it with previous geometric schemes; Schofield 1989 : fig. 1 ), was referring sicuro the theory of the perfect number. It is worth emphasizing again that the use of such numbers was topical per the 1480s and 1490s, after the publication of Euclid’s Elementa with commentary by Giovanni Campano (Venice 1482). I would add that the number 28 (the same as the number of coffers con each ring of the dome of the Pantheon) had already determined the number of episodes of Giotto’s ‘Life of Saint Francis ‘ per Assisi upper church and the panels of the north doors of the Baptistery of Florence. Durante the sixteenth century, this number would establish (together with the number 6) the proportions of the Florentine Viadotto Santa Trinita by Bartolomeo Ammannati (see Di Teodoro et al. 1981 ).

## Author’s Libretto

The preparation of Figures 6 , 8 and 9 is credited to Filippo Camerota. The study of Leonardo’s drawings, Ms. B, ff. 24r (Fig. 6 ), 19r-18v (Fig. 8 ), and 18r-17v (Fig. 9 ) is credited puro the collaboration between the writer and Filippo Camerota. Ursula Zich has redrawn some of my graphics on the elaboratore. The transcriptions of Leonardo’s various steps follow conservative criteria; I simply distinguished u from v sopra the celibe grapheme u/v. The ‘a’ verb (third person singular, present indicative of the verb ‘sicuro have’) has been rendered with an ton (a). Abbreviations are enclosed mediante parentheses; brackets enclose additions.

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