It describes how the crusaders used 11 trebuchets to attack the Maledicta Tower of Acre between June and July 1191.

(n.b. The account uses the term "Turk" throughout, where later sources would use "Saracen". It does not refer to the population of modern Turkey.)

Nothing could stand against the power of this machine. It hurled huge stone-shot: “violent action, far-hurled stones; the blow smashed everything, whatever it struck.” If the stones met no obstruction when they fell, they sank a foot deep into the ground.
This machine struck some of our trebuchets and smashed them to pieces or at least rendered them unusable. Its shots also destroyed many other siege machines, or broke off what it hit. It shot with such force, and its blows were so effective, that no material or substance could withstand the unbearable impact without damage, no matter how solid or well-built it was."

The account then moves to the besieging crusaders' machines:
" The king of France ... concentrated on constructing siege machines and placing trebuchets [ petrariae] in suitable places. He arranged for these to shoot continually day and night. He had one excellent one which he called “Bad Neighbour” [Malvoisine].
The Turks in the city had another which they called “Bad Relation” [Mal Couisine] and often used to smash “Bad Neighbour” with its violent shots. The king kept rebuilding it until its continual bombardment partly destroyed the main city wall and shattered the Cursed Tower.

On one side the duke of Burgundy’s trebuchet had no little effect. On the other the Templars’ trebuchet wreaked impressive devastation, while the Hospitallers’ trebuchet also never ceased hurling, to the terror of the Turks.

Besides these, there was a trebuchet that had been constructed at general expense, which they called “God’s Stone-Thrower”. A priest, a man of great probity, always stood next to it preaching and collecting money for its continual repair and for hiring people to gather the stones for its ammunition. This machine at last demolished the wall next to the Cursed Tower for around two perches’ length [10 metres].

The Count of Flanders had had a choice trebuchet, which King Richard had after his death, as well as another trebuchet which was not so good. These two constantly bombarded the tower next to a gate which the Turks frequently used, until the tower was half-demolished.

Besides these, King Richard had two new ones made with remarkable workmanship and material which would hit the intended target no matter how far off it was... He also had two mangonels [traction trebuchets?] prepared.
One of these was so swift and violent that its shots reached the inner streets of the city meat market.
King Richard’s trebuchets hurled constantly by day and night. It can be firmly stated that one of them killed twelve men with a single stone.
That stone was sent for Saladin to see, with messengers who said that the diabolical king of England had brought from Messina, a city he had captured, sea flint and the smoothest stones to punish the Saracens.
Nothing could withstand their blows; everything was crushed or reduced to dust."

To move away from the “Itinerarium Peregrinorum “ for a moment, Imad al-Din, in his account of the siege from the other side, said that the walls were left “no higher than a man’s height.” He then continued:
“They [the crusaders] engaged in the discharge of trestle-framed trebuchets [manjaniqat], the erecting of siege machines and pole-framed trebuchets ['arradat], and the loading of stones until the wall was on the verge of destruction. The walls were shaken loose, breaches were visible, and the curtain walls were demolished.”

Though the common mob in the crusader army were enraged at rumours of it, on 12th July the city negotiated a surrender & the garrison walked out. Prominent citizens were given as hostages on the promise that Christian prisoners were to be released and (impossibly) that the Holy Cross was to be handed over to the crusaders. The deadline came and went…
On 20th August Richard the Lionheart ordered the execution by beheading of 2700 of the hostages. It was duly carried out.