"Focus Your Heart on the Holy of Holies" - an Excerpt from Jewish Literature - Mishnah (Second Century CE)
"...Rabbi Eliezer says: One who makes his prayer "set" [as though it is burdensome to him], his prayer does not constitute "pleading" [for Divine mercy]. Rabbi Yehoshua says: One who is traveling in a dangerous place should offer a brief prayer [and] say: Save, G-d, Your people, the remnant of Israel; at every period of transition let their needs be before You. You are the Source of all blessing, G-d, Who heeds prayer.
If one was riding a donkey, he should dismount from it [while he prays]. And if he is unable to dismount, he should turn his face [towards Jerusalem]. And if he is unable to turn his face, he should focus his heart toward the Holy of Holies [in the Temple in Jerusalem]. If one was sitting in a boat, or in a wagon, or on a raft, [when he prays] he should focus his heart toward the Holy of Holies...
[One] should not stand up to pray unless he is in a serious frame of mind. The original pious ones used to wait one hour and then pray, in order to direct their hearts towards the Omnipresent. [While one is reciting Shemoneh Esrei,] even if the king greets him, he should not respond to him, and even if a snake wraps around his heel, he should not interrupt... They used to say about him, about Rabbi Chanina ben Dosa: When he would pray for the sick, he would say: This one will live and this one will die. They said to him: How do you know? He replied to them: If the prayer is fluent in my mouth, I know that it has been accepted; and if not, then I know that it has been torn up..." (Mishnah, Berachot 4-5)