Pius IX on proclaiming the dogma of the Immaculate Conception: "the Vicar of God had need of a special grace or else he would have died of love through his knowledge and the tremendous flood of exalted feeling."

From Chapter X​ of Fr Francis Thornton's Cross Upon Cross: The Life of Pope Pius IX:

​"...Both Scripture and history threw the lie in the teeth of Mary's enemies and the Pope's detractors. The angel Gabriel had said to Mary in greeting, "Hail full of grace!" Had she been stained with original sin at the time of the angel's appearance the greeting would have been untruthful and vain. It remained for theology to establish in what manner it was truthful...

...Now toward the end of the Year of Jubilee in 1854, the work on the promulgation of the dogma was over...

...The morning of the 8th of December, 1854 was clear and beautiful. The blue of the Queen of Heaven was stretched like a great tent of light from horizon to horizon. At dawn, and even before the first light, crowds of people had come to Saint Peter's piazza where they camped in their thousands. Those ​fortunate enough to have tickets of admission crowded into the great basilica glowing with the lights of thousands of candles suspended in crystal chandeliers from the brilliant arches of the great temple...

...The Pope himself has left us a memorial of the morning in a conversation with Mother Mary Macchi, a personal friend of the Holy Father. She was a nun of Santa Trinita dei Monto, a convent the Pope loved to visit. Once after dinner at the convent, the nuns asked the Holy Father to tell them what he had felt in defining the dogma of the Immaculate Conception. After a moment or two of recollection, the Pope replied:

"What I experienced and felt in defining the dogma cannot be fully expressed. When I began the promulgation I felt that my voice was too weak to be heard by the immense crowd [at least fifty thousand people] in the Vatican Basilica. But when I came to the formula of definition God gave his Vicar such power and strength that his voice filled the whole basilica. I was so moved by this, that I was forced to stop speaking for a moment while tears rained down my cheeks. While God proclaimed the dogma through the mouth of His Vicar He made me see so clearly and fully the incomparable purity of the Blessed Virgin that deep down in my spirit my soul was overwhelmed with joy beyond this earth...I do not fear to assert the Vicar of God had need of a special grace or else he would have died of love through his knowledge and the tremendous flood of exalted feeling."