Yeh, seems it all stems from an anecdote from Karasowski and repeated by Niecks:
'From contemporary observers we learn with what perseverance he laboured to overcome the technical difficulties of the pianoforte. Impressed by the good effect of an extended chord, but unable to play it with his small hand, he endeavoured to produce the desired expansion by a mechanical contrivance of his own manufacture, which he kept between his fingers even during the night.' Karasowski, pg 22.
'From the place and wording of Karasowski's account
it would appear that this experiment of Chopin's took place
at or near the age of ten.' – Nieks, pg 56
Eigeldinger steers well clear of it - that speaks volumes.
Nieks carries on:
'Of course it does not matter much whether we know or do not know the year or day of
the adoption of the practice, what is really interesting is the fact itself. '
Though I'm not so sure he's accepting the 'fact' himself. Quite suspiciously he next says:
'I may, however, remark that Chopin's love of
wide-spread chords and skips, if marked at all, is not strongly
marked in the Variations on the German air and the first
Rondo. Let the curious examine with regard to this matter
the Tempo di Valse of the former work, and bars 38 — 43 of
the Pill lento of the latter. In the Rondeau a la Maznr, the
next work in chronological order, this peculiarity begins to
show itself distinctly, and it continues to grow in the works
that follow. It is not my intention to weary the reader with
microscopical criticism, but I thought the first manifesta-
tions of Chopin's individuality ought not to be passed over in
silence.'
Check 'em out - lots of rolls.