Begun at Florence, in the house of Piero di Braccio Martelli, on the
22nd day of March 1508. And this is to be a collection without
order, taken from many papers which I have copied here, hoping to
arrange them later each in its place, according to the subjects of
which they may treat. But I believe that before I am at the end of
this [task] I shall have to repeat the same things several times;
for which, O reader! do not blame me, for the subjects are many and
memory cannot retain them [all] and say: 'I will not write this
because I wrote it before.' And if I wished to avoid falling into
this fault, it would be necessary in every case when I wanted to
copy [a passage] that, not to repeat myself, I should read over all
that had gone before; and all the more since the intervals are long
between one time of writing and the next.

[Footnote: 1. In the history of Florence in the early part of the
XVIth century _Piero di Braccio Martelli_ is frequently mentioned as
_Commissario della Signoria_. He was famous for his learning and at
his death left four books on Mathematics ready for the press; comp.
LITTA, _Famiglie celebri Italiane_, _Famiglia Martelli di
Firenze_.--In the Official Catalogue of MSS. in the Brit. Mus., New
Series Vol. I., where this passage is printed, _Barto_ has been
wrongly given for Braccio.

2. _addi 22 di marzo 1508_. The Christian era was computed in
Florence at that time from the Incarnation (Lady day, March 25th).
Hence this should be 1509 by our reckoning.

3. _racolto tratto di molte carte le quali io ho qui copiate_. We
must suppose that Leonardo means that he has copied out his own MSS.