From the 1859 Stewart bio, page 61.

M. Tissendorf also lately discovered in a certain monastery in Egypt the Old Testament and part of the New, as well as the 1st Book of Hermas, all of which were written in the 2nd Century, or 1750 years ago. This MS. is represented to be in excellent condition. From this we may conclude that parchment manuscripts may be preserved for almost on unlimited period, for those that are kept in the Museums, even though they exceed 1000 years, have not lost a single letter. Nor is it all surprising that manuscripts on parchment should have been preserved for so long a time; for it must be admitted to be much more wonderful that the papyrus manuscripts which are so much more fragile than skins, should have come down to our times, well preserved, many of them more than 3000 years old. Those who please may at the British Museum and at Turin see many of them; even this is nothing startling, for corn and many other seeds have been found in Egyptian coffins which have been underground for perhaps 4000 years, and have not in the least lost their germinal powers. Many locks of hair, too, have been found in these coffins, preserved in a most perfect condition till the present day.
Simonides was countering a skeptical sentiment to his discoveries. The next was in 1861.

It may not be generally known, but it is an undoubted fact, that no MSS. of any kind, if we except the Hieratic papyri, are known to ascend to the first or second century, and that of those of the fourth or fifth there are not more than five or six throughout all the libraries of Europe; yet M. Simonides, if he is to be believed, has got these wonders “plenty as blackberries,” there being, as it would seem, no limit to the treasures with which he kindly proposes to flood the world.

Athenaeum
https://books.google.com/books?id=GsQ2AQAAMAAJ&pg=PA756
In the Dec 9 issue, Henry Stobart offered a caveat to this:

P.S. I think you are in error in a statement that “ it is an undoubted fact that no MSS. of any kind, if we except the Hieratic papyri, are known to ascend to the first or second century.” I brought home with me from Egypt in 1855, I think, four wooden tablets covered with manuscript, written upon a kind of cement, which contained a series of aslrouomical observations, in the Demotic character, made in the reigns of Trajan and Hadrian. They are in Mr. Mayer's Museum, and have been translated by Dr. Brugsch of Berlin, and published both in English and French—the observations having been submitted both to Mr. Airy and to M. Biot, and their truth confirmed by them.

Athenaeum
The Mayer Manuscripts
https://books.google.com/books?id=pRJEAAAAcAAJ&pg=PA807
The Athenaeum accepted the correction:

We meant to say that no such MS. as the fac-similes of M. Simonidus are known to exist Of course Coptic Papyri exist; but about this class of document there is no discussion whatever.
And this came up in the letter below.

The irony card was played the same month by Simonides, at a time when it was well-known in London (as per the Hort letter) that Simonides asserted his involvement in making Sinaiticus:

It is to be regretted that you see no cause for thankfulness to God in the discovery of the earliest MSS. of the New Testament extant; and I fear Mr. Tischendorf came in for a share of your animadversions for the praise which he offered to God for his discovery of the ‘Codex Sinaiticus.’

The Athenaeum, December 21, 1861, p.849
https://books.google.com/books?id=KmVDAQAAMAAJ&pg=PA849