Not only did Calvin teach and preach without any notes, he did so directly from the original language:
Calvin would then read a text in Hebrew or Greek, and offer a very literal translation of it into Latin. After that, he would provide a smoother Latin translation, followed by his commentary. Jean Crispin, a publisher of Calvin’s day, attended some of the reformer’s lectures. He commented on Calvin’s lecture style as follows: ‘… but he kept on lecturing continuously for a full hour and did not write down one single word in his book to help his memory.’ The book in question was the Hebrew Old Testament and, thus, Calvin was sight-reading the Hebrew text without any linguistic aids. Then, also without notes, he made comment on the text that had been read.
Colladon also remarked on Calvin’s teaching style; he said:
When lecturing, he always had only the bare text of Scripture; and yet, see how well he ordered what he said! Even when (some years before his death) he was lecturing on Daniel, although at some places he had to narrate historical facts at length, as we see from the lectures, he never had any paper before him as an aide-mémoire. And it was not as if he had adequate time to prepare; for, whatever he may have wished, he simply had not the opportunity. To say the truth, he usually had less than an hour to prepare.
John D. Currid, Calvin and the Biblical Languages (Fearn, Ross-shire, UK: Christian Focus Publications, 2006), 47.